By Sylvia Westall and Warren Strobel
KUWAIT, Jan 15 (Reuters) - Western and Gulf Arab nations pledged more than $2.4 billion on Wednesday for U.N. aid efforts in Syria, where a near three-year civil war has left millions of people hungry, ailing or displaced.
The pledge arose from a U.N. appeal for $6.5 billion in 2014, which was launched last month and is the largest in the organization's history.
The world body estimates the conflict has reversed development gains in Syria by 35 years, with half its people now living in poverty.
But only around 70 percent of $1.5 billion pledged at a similar meeting last year has reached U.N. coffers, hinting at donor fatigue with no end to the bloodshed on the horizon.
U.N. humanitarian chief Valerie Amos said all sides in the conflict had shown "total disregard for their responsibilities under international humanitarian and human rights law".
"Children, women, men are trapped, hungry, ill, losing hope," Amos told the 69 countries attending a donor conference held in Kuwait.
The Gulf state's ruling emir, Sheikh Sabah al-Ahmed al-Sabah, promised $500 million in new aid, while the United States announced a contribution of $380 million.
Qatar and Saudi Arabia pledged $60 million each. The European Union pledged $225 million and Britain $165 million.
U.N. Secretary-General Ban Ki-moon said the total was more than $2.4 billion.
Money raised last year in Kuwait was used by the United Nations to provide food rations, medicine, drinking water and shelters for people in Syria and surrounding countries.
The largest donations at that conference came from Gulf Arab governments, which have mainly backed Syrian rebels trying to oust President Bashar al-Assad.
Kuwait has avoided showing support for either side and has voiced concern about the sectarian nature of the conflict.
"Even under the best circumstances, the fighting has set back Syria years, even decades," said Ban, who chaired the conference.
"I am especially concerned that the sides are using violence against women and girls to denigrate and dehumanize their opponents. I call for an immediate end to these abuses, which harm individuals and undermine Syria's future."
Ban has previously expressed regret that not all the promised donations have been received from the last meeting, with 20-30 percent still lacking.
He told the gathering he hoped peace talks due to start in Switzerland on Jan. 22 would bring the Syrian government and opposition to the negotiating table - although Assad's adversaries are deeply split over whether to attend.
"I hope this will launch a political process to establish a transitional governing body with a full executive powers, and most importantly, end the violence," he said.
He urged the opposition forces to come with a united delegation. He added organisers had not been able to finalize whether Iran, Syria's Shi'ite Muslim ally, would take part and was coordinating closely with Russia and the United States.
The World Food Programme (WFP) said on Tuesday it had delivered rations to a record 3.8 million people in Syria in December, but civilians in eastern provinces and besieged towns near the capital remain out of reach.
The U.N. agency voiced concern at reports of malnutrition in besieged areas, especially of children caught up in the fighting, and called for greater access.
Shooting forced the United Nations to abort a delivery of food and polio vaccines to one besieged district of Damascus after Syrian authorities said it should use a circuitous and dangerous route, a spokesman said on Wednesday.
Aid workers in Syria have accused authorities of hampering deliveries to opposition-controlled areas and threatening groups with expulsion. Damascus blames rebel attacks for aid delays.
The WFP says it needs to raise $35 million every week to meet the food needs of people both inside Syria and in neighboring countries.
U.S. Secretary of State John Kerry said on Monday that Syria's government and some rebels might be willing to permit humanitarian aid to flow, enforce local ceasefires and take other confidence-building measures. (Writing by Rania El Gamal; Editing by William Maclean and Alison Wililams)