WASHINGTON: U.S. officials Wednesday urged international donors to make good on pledges of more than $1.5 billion in aid for Syrians, warning that millions of people remained in dire need as the war rumbles on.

There are now some 763,000 refugees who have fled Syria for neighboring countries, while another 2.5 million are estimated to have been displaced inside the country.

But the United Nations warned the same day that the number of people fleeing the fighting could reach 1.1 million by June, and described a certain crisis “fatigue” among developed nations over the conflict.

The United States is providing some $365 million in assistance for food and shelter for Syrians caught up in the 22-month war to oust Syrian President Bashar Assad, in which more than 60,000 people have been killed.

“Bottom line, there hasn’t been enough and we need to collectively, as an international community, press for more access,” USAID assistant administrator Nancy Lindborg told reporters on a conference call.

She and Assistant Secretary for Refugees Anne Richard have just returned from visiting Syrian refugee camps in Turkey and Jordan. They also watched refugees, under cover of darkness, cross from Syria into Jordan.

Some 80 percent of the refugees are women and children, while 67 percent of the refugees live outside of the camps, they said.

“I’d never seen people become instant refugees,” Richard said, adding it was very emotional “to see kids in the middle of the night, up way too late, bundled up against the cold and the whole family’s possessions shrunk down to a suitcase.”

But it was also good to see children safe and secure, playing in a well-organized refugee camp in Turkey, which has been helped by U.S. aid, she added.

A week ago, an international donors meeting in Kuwait pledged more than the targeted $1.5 billion in aid for affected Syrians.

Addressing the conference, U.N. chief Ban Ki-moon called for urgent financial aid, warning if funds were not forthcoming “more Syrians will die.”

Washington was urging other countries to step forward “because the needs are so great, this cannot be shouldered by any one country, especially as we’re looking at the impact in the neighboring countries,” Lindborg said.

Inside Syria, one of the key issues is getting access to communities that have been cut off by the fierce fighting, they added.

One U.N. convoy last week managed to negotiate safe passage across the Syrian government and the opposition’s front lines to reach stricken communities in the north who had received no aid so far.

The convoy brought some 2,000 tents and 12,000 blankets to people who had been living in flimsy shelters.

But the American officials also denied reports that some of the aid would fall into the hands of the regime.

“We keep going back and double checking ... to make sure that nothing is being diverted. Nothing is going to benefit the regime, and we’re satisfied today that all the aid is going to benefit the civilians in Syria,” Richard said.