High Commissioner for Refugees Antonio Guterres said the "moment of truth" was approaching for the region as the risk of the Syrian conflict expanding beyond the country's borders was escalating.
"The humanitarian situation is dramatic beyond description," he said. "The refugee crisis is accelerating at a staggering pace, month after month."
Jordanian Foreign Minister Nasser Judeh said during a mid-February meeting in Washington with Secretary of State John Kerry that Jordan was trying to address the needs of the estimated 360,000 Syrians who've fled to Jordan.
Guterres said Syrians were leaving the country at a rate of 40,000 per week since early January. As of Monday, there were around 940,000 Syrians registered as refugees across the Middle East and North Africa.
"Countries of asylum have been very generous and kept their borders open but their capacity to do so is under severe pressure," he said.
Kerry said from Italy that the U.S. government was offering $60 million in non-lethal assistance for the Syrian opposition.
Syrian President Bashar Assad, Kerry said, has long ago lost his legitimacy to lead and he must be removed from power.
"Assad cannot shoot his way out of this," he said.