By Alastair Macdonald
UKRAINIAN-RUSSIAN FRONTIER, March 18 (Reuters) - Ukraine has strengthened frontier defenses with Russia following Moscow's seizure of Crimea but there is no sign of a major troop build-up in a region where some say they would welcome a Russian takeover.
On a day when a Ukrainian soldier became the first fatal casualty in the confrontation on the Black Sea peninsula, at the southernmost crossing between the two countries, where Ukraine dug anti-tank ditches this week, Kiev's frontier guards were keen to play down the Russian threat and hope for the best.
"I think everything will be all right in the end," said Sergeant Oleksy Romanenko, as he lifted a barrier to let in one of a slow trickle of cars arriving from Russia on Tuesday.
But despite President Vladimir Putin saying Moscow had no designs on regions of Ukraine beyond Crimea, tension persists.
Asked how he felt about possibly having to fight former Soviet allies who Ukraine's president says are ready to invade, Romanenko said tersely: "We are ready to defend our country."
Border defenses have been strengthened by an anti-tank chicane of house-high concrete blocks, placed across the two-lane M14 highway that links the Russian city of Rostov-on-Don and runs round the coast toward Crimea, 350 km (200 miles) west.
Mechanical diggers built a ditch and earthwork rampart stretching out several hundred meters on either side of the border post earlier this week. Officials have been keen to show it to media as a sign of their resolve to keep Russia out.
But along its remaining 2,000 km, the frontier is scarcely visible across the vast, rolling farmland of the steppe.
Apart from the border guards overseeing the customs post and checking documents, there was no sign of armed activity, even as Ukraine's prime minister was saying the conflict had moved from a political to a military stage. Small detachments of military trucks and a few armored vehicles have been seen by journalists moving in the area in recent days, but not large units.
The new authorities in Kiev are calling up recruits to an army they say was neglected under ousted, Moscow-backed president Viktor Yanukovich. But Ukraine's armed forces remain heavily outnumbered and outgunned by their Russian neighbors.
Border guards have been more concerned to prevent what Kiev calls "Kremlin agents" entering from Russia - provocateurs they blame for violent street clashes in the mainly Russian-speaking eastern cities of Donetsk and Kharkiv. Their goal, Ukraine says, is to turn local people against leaders in Kiev and justify Moscow moving to "protect" ethnic Russians, as in Crimea.
Captain Ihor Lizohub, deputy commander at the crossing, said Russians seeking entry were being asked their reasons: "Those who deliberately give false information are turned away."
He played down tensions with Russia forces up the road, saying the two border posts maintained contact by telephone.
People using the crossing on Tuesday - perhaps 20 in all in the course of an hour - were anxious about the situation, but more troubled by the threat of economic disruption than war.
"No one wants war," said 40-year-old Russian businessman Sergei Alexandrovich from Rostov, who had been visiting family in Ukraine. "We've got very good economic relations. It would be very bad for business if the border closes."
There was already some inconvenience. A Ukrainian motorist, Alexander, said he tried to get into Russia to fill his car with cheaper fuel but was turned back by Russian guards who demanded he purchase expensive additional vehicle insurance.
Many people living in eastern Ukraine are native Russian speakers and see themselves as closer to Russians across the border than to Ukrainian-speakers in the west of their country. Some agree with Putin that the new government in Kiev, which includes right-wing nationalists, is both illegal and fascist.
Calls for a referendum similar to that in Crimea are common. Many people stop short of seeking Crimean-style union with Russia but want more autonomy for the heavily industrialized and heavily populated eastern regions of the Donbass coalfield.
"Give us a referendum," said Gennady, 47, who runs a cafe by a border post whose very existence angers him. "There was no border here in the Soviet Union. Thank you, Mr. Gorbachev."
The collapse of the Soviet state under Mikhail Gorbachev in 1991 remains a bitter memory for many in eastern Ukraine.
In the regional capital Donetsk on Tuesday, representatives of Russian-speaking movements met a senior official of the local assembly to try to defuse tensions that have led to violence.
Activists called for a working group to draw up a plan to hold a referendum on devolution in the coming months. "We want the Soviet Union, with Russia," said Natalia Belotserkovskaya of the Russian Bloc, who attended the talks in Donetsk.
There is little to suggest that tensions, both within Ukraine and with Russia, will dissipate quickly. In the meantime conditions at the border crossing remain difficult for some.
Vadim Pavlotsky from Moscow is visiting relatives in Ukraine for a few weeks and wanted to make a day-trip back across the border on Tuesday. The 24-year-old was told Ukrainian guards, on the lookout for young militants, might well not let him back.
"This is a tense situation," he said. "It's all a political game in which ordinary people are suffering." (Editing by Mark Heinrich)