By Adrian Croft and Gabriela Baczynska
NEWPORT, Wales/DONETSK, Ukraine, Sept 4 (Reuters) - Ukrainian President Petro Poroshenko and the main pro-Russian rebel leader said they would both order ceasefires on Friday, provided that an agreement is signed on a new peace plan to end the five-month war in Ukraine's east.
The breakthrough came after a week in which the pro-Moscow separatists scored major victories with what NATO says is the open support of thousands of Russian troops.
Speaking on the sidelines of a NATO summit in Wales, Poroshenko said the ceasefire would be conditional on a planned meeting going ahead in Minsk on Friday of envoys from Ukraine, Russia and Europe's OSCE security watchdog.
"At 1400 local time (1100 GMT on Friday), provided the (Minsk) meeting takes place, I will call on the General Staff to set up a bilateral ceasefire and we hope that the implementation of the peace plan will begin tomorrow," he told reporters.
Alexander Zakharchenko, head of the main rebel Donetsk People's Republic, said in a statement his men would also order a ceasefire, from one hour later, provided that Kiev's representatives signed up to a peace plan at the Minsk meeting.
There have been local agreements to hold fire, for example during the recovery of bodies from a Malaysian airliner shot down over rebel territory in July, but Thursday's announcements were the first time the two sides have called for a full truce.
Rebels still expressed skepticism. Oleg Tsaryov, a senior rebel official, told Reuters the separatist truce would depend on the government providing guarantees, "because in the past we had some ceasefire agreements Poroshenko didn't honor".
A source close to Zakharchenko said government forces bombarded Donetsk within 15 minutes of Poroshenko's announcement of the ceasefire plan: "We'll see how the talks go tomorrow, but it won't be easy. All this talk of truce amid more and more shelling."
The announcements come a day after Russia's President Vladimir Putin put forward a seven-point peace plan, which would end the fighting in Ukraine's east, bring in outside monitors and aid, while leaving rebels in control of their territory.
To keep the pressure up on Russia, a White House official attending the NATO summit said the United States was preparing a new round of economic sanctions, but progress towards a truce could halt new European financial sanctions that EU leaders had been expected to agree on Friday. French President Francois Hollande said the decision on the sanctions package would depend "on the coming hours".
There is no sign of a halt in fighting in the east, where rebels have rapidly advanced in the past week, backed by what Kiev and NATO say is the support of thousands of Russian troops with artillery and tanks. Moscow denies its troops are there.
COLUMNS OF SMOKE
Reuters journalists heard explosions and saw columns of smoke on the eastern outskirts of Mariupol, a government-held port of 500,000 people that is the next big city in the path of the rebel advance. A Ukrainian military source said troops were bracing for a potential attack on the city.
Government shells rained down overnight on a residential district of Donetsk, capital of one of the rebels' two self-proclaimed independent states.
The West has backed Kiev by imposing economic sanctions on Moscow, but has also made clear it will not fight to protect the country, where pro-Russian rebels rose up in two provinces after Moscow annexed the Crimea peninsula in March.
Poroshenko was invited to meet U.S. President Barack Obama, Germany's Angela Merkel, France's Francois Hollande and other Western leaders at the NATO summit in Wales, hosted by Britain's David Cameron.
The summit stage was set with harsh words for Russia: "To the east, Russia has ripped up the rule book with its illegal, self-declared annexation of Crimea and its troops on Ukrainian soil threatening and undermining a sovereign nation state," Obama and Cameron wrote in a joint newspaper editorial.
But after the announcement of the potential ceasefire, Western officials appeared to take a softer line. German Foreign Minister Frank-Walter Steinmeier said he was moderately optimistic that de-escalation could be achieved.
The prospect of a ceasefire could also give France an opportunity to reverse a decision to postpone the delivery of a French helicopter carrier warship to Russia, due next month.
"What are the conditions (of delivering the ship)? A ceasefire and a political settlement. Today those conditions are not in place," Hollande said. If there were further complications the delivery would be delayed, but the contract would not be suspended, he added.
Moscow had accused him of caving in to U.S. political pressure: "France's reputation as a reliable partner that carries out its contractual obligations has been thrown into the furnace of American political ambitions," Russian Foreign Ministry deputy spokeswoman Maria Zakharova wrote on Facebook.
The past few days have seen conflicting signals from both Moscow and Kiev. Putin made a number of belligerent statements over the past week before unveiling his peace proposal on Wednesday and discussing it by telephone with Poroshenko.
The Ukrainian leader hinted at a possible ceasefire on his website on Wednesday, but that wording was later dropped. His prime minister, Arseny Yatseniuk, derided Putin's peace proposal as a "deception" and said Putin's real aim was to "destroy Ukraine and restore the Soviet Union".
Ukraine has previously refused to discuss any political deal with the rebels, calling them terrorists and proxies of Moscow. But with the hope evaporating of a swift victory, Poroshenko may have felt it is now time to hear the Kremlin's offer.
This week the rebels dropped a demand for full independence and said they would accept some kind of special status in Ukraine. That lifts one of the main obstacles to peace talks.
Russian Foreign Minister Sergei Lavrov discussed the ceasefire with his French and German counterparts, and accused Washington of trying to undermine the nascent peace process.
Putin's peace offer would leave rebels in control of territory that accounts for a tenth of Ukraine's population and an even larger chunk of its industry. It would also require Ukraine to remain unaligned. Kiev had said last week it would try to join NATO, although full membership is unlikely since several members oppose it.
The rebels said they would agree as part of the ceasefire to allow a humanitarian corridor for aid and refugees. The truce would be monitored by observers from the Organization for Security and Cooperation in Europe.
On the ground, there has so far been no sign yet of any ceasefire. Government forces shelled the southern outskirts of the rebel bastion of Donetsk overnight.
Houses in Donetsk's leafy Petrovka district were pockmarked with shrapnel. Residents had sought refuge in a bomb shelter.
"I don't think they can reach any agreements now. Each side comes up with conditions unacceptable for the other. And so we get shelled," said Lena, who declined to give her surname.
Reuters journalists saw a rebel column including a tank driving south from Donetsk towards the village of Berezovo. Residents said three burnt out military trucks in the village had carried Ukrainian troops that came under attack.
Government troops had been on the offensive since Poroshenko took office in June, squeezing the rebels into two provincial capitals, Donetsk and Luhansk. But last week the rebels turned the tide with an advance along the coast of the Sea of Azov.
A NATO officer, speaking on condition of anonymity, said NATO believed several thousand Russian troops were in Ukraine with hundreds of tanks and armored vehicles. (Additional reporting by Aleksandar Vasovic in Mariupol, Pavel Polityuk and Gareth Jones in Kiev, Katya Golubkova and Timothy Heritage in Moscow and Kylie MacLellan in Newport; Writing by Peter Graff; Editing by Giles Elgood and Will Waterman)
09/06/2014 6:08 PM EDT
Factory Ablaze After Artillery Fire Near Mariupol
Prolonged artillery fire was heard late on Saturday to the east of the port of Mariupol in eastern Ukraine, a Reuters reporter said, in what may be the first significant violation of a ceasefire declared little more than 24 hours earlier.
The reporter saw an industrial facility, a truck and a gas station ablaze in an area within the limits of Mariupol, a city of 500,000 people on the Sea of Azov near the Russian border.
The area had seen fierce fighting between Ukrainian government forces and pro-Russian separatists before the ceasefire took effect on Friday evening. It had been quiet since then until the artillery fire began late on Saturday.
"There has been an artillery attack. We received a number of impacts, we have no information about casualties," a Ukrainian officer told Reuters at the scene.
09/06/2014 6:03 PM EDT
Ukraine Battalion: Reports Of Civilian Casualties In Shelling
09/06/2014 6:00 PM EDT
#RussiaViolatedCeasefire Trends On Twitter
Twitter users are using the hashtag #RussiaViolatedCeasefire to blame Moscow for renewed violence in east Ukraine.
Hashtag #russiaviolatedceasefire is now showing up as a suggestion. Good work, fellow Ukrainians— неХуёвый Portland (@the_boris) September 6, 2014
Meanwhile, Lithuanian Ambassador to Sweden Eitvydas Bajarunas used the hashtag for call for more information, as rockets and shelling were reported in the Ukrainian port city of Mariupol.
09/06/2014 5:43 PM EDT
Rockets Fired In Ukraine Amid Ceasefire
Witnesses in the Ukrainian port city of Mariupol are reporting sustained explosions outside the city and a volunteer battalion of Ukrainian fighters says Grad rockets are being fired at its positions.
The reports Saturday night come little more than a day after Ukraine and Russian-backed separatist rebels signed a cease-fire after more than four months of fighting in the country's east.
The cease-fire had appeared to largely been holding during much of the day.
But late Saturday, witnesses in Mariupol told The Associated Press by telephone that heavy explosions were coming from the city's eastern outskirts, where Ukrainian troops retain defensive lines against the rebels.
The volunteer Azov Battalion said on Facebook that their positions were hit by Grad rockets, but did not give details.
09/06/2014 4:49 PM EDT
Reports Of Shelling In Mariupol
BBC journalists Fergal Keane and Will Vernon in Ukraine's Mariupol say that shelling of the port city has resumed.
#Ukraine shelling started at approx 2235 local and is continuing— Fergal Keane (@fergalkeane47) September 6, 2014
#Ukraine On roof of hotel and can see flashes from explosions and hear powerful detonations.— Fergal Keane (@fergalkeane47) September 6, 2014
09/06/2014 12:21 PM EDT
ICRC Says Aid Trucks Forced Back By Shelling
The International Committee of the Red Cross said its aid trucks were forced to turn back on Saturday morning due to shelling in east Ukraine.
09/06/2014 10:59 AM EDT
Putin, Poroshenko Agree Cease-Fire Holding
Russian President Vladimir Putin and Ukraine's President Petro Poroshenko agreed on Saturday in a telephone call that a ceasefire in eastern Ukraine was generally holding but said further steps were needed to make it more durable.
The ceasefire between Ukrainian government forces and pro-Russian separatists took effect on Friday evening, part of a wider peace plan aimed at ending five months of fighting in eastern Ukraine.
"(The two leaders) also stressed the need for the maximum involvement of the Organisation for Security and Cooperation in Europe (OSCE) in monitoring the situation ... and for cooperation in providing Ukrainian and international humanitarian help," Poroshenko's office said in a statement.
09/06/2014 10:58 AM EDT
Rebel Leader: Prisoner Exchange To Take Place Saturday
A separatist leader said that the rebels and Ukrainian government will begin the exchange of prisoners of war, part of the peace roadmap, later on Saturday, Reuters reports. Meanwhile, Kiev said the details of the exchange were still being worked out.
09/05/2014 12:38 PM EDT
Peace Deal Outlined
New York Times Moscow bureau chief Neil MacFarquhar outlines the different aspects of the Ukrainian peace deal.
The Ukrainian National Information Agency released a list of the 14 points included in the cease-fire plan. #Ukraine— Neil MacFarquhar (@NeilMacFarquhar) September 5, 2014
2 some focused on cease-fire itself, some on practical steps to get the government functioning and some on Donbas political future. #Ukraine— Neil MacFarquhar (@NeilMacFarquhar) September 5, 2014
3 The agreement followed almost verbatim a cease-fire proposal first put out by Mr. Poroshenko in June.— Neil MacFarquhar (@NeilMacFarquhar) September 5, 2014
4 14 points include amnesty for all those who disarm and who did not commit serious crimes, as well as the release of all hostages. #Ukraine— Neil MacFarquhar (@NeilMacFarquhar) September 5, 2014
5 Militias will be disbanded, and a 10-kilometer buffer zone established along Russian-Ukrainian border. Area subject to joint patrols— Neil MacFarquhar (@NeilMacFarquhar) September 5, 2014
6 Separatists agreed to leave administrative buildings they control and broadcasts from Ukraine to resume on TV #Ukraine— Neil MacFarquhar (@NeilMacFarquhar) September 5, 2014
7 On future, the agreement said power would be decentralized and the Russian language protected. Region consulted on selection of governor— Neil MacFarquhar (@NeilMacFarquhar) September 5, 2014
8. Early elections and jobs....No mention of a chicken in every pot. #Ukraine— Neil MacFarquhar (@NeilMacFarquhar) September 5, 2014
09/05/2014 12:18 PM EDT
Obama: Hopeful But Skeptical
U.S. President Barack Obama said he was hopeful but skeptical about a ceasefire agreed in Ukraine on Friday and urged European allies to agree on new sanctions against Russia that could be suspended if the peace plan holds.
He also said he was leaving a two-day NATO summit in Wales confident that U.S. allies were prepared to join a broad coalition to take action to degrade and ultimately destroy Islamic State militants in Iraq.
"We also sent a strong message to Russia that actions have consequences. Today the United States and Europe are finalizing measures to deepen and broaden our sanctions across Russia's financial, energy and defense sectors," Obama told a news conference.
NATO had made clear it would defend every ally, and that it supported Ukraine's sovereignty against what he called Russian aggression, he said.
"With respect to the ceasefire agreement, obviously we are hopeful but based on past experience also skeptical that in fact the separatists will follow through and the Russians will stop violating Ukraine's sovereignty and territorial integrity. So it has to be tested," the president said.