The head of the opposition Syrian National Coalition on Thursday called on the United States to help set up safe havens inside Syria in areas under rebel control, AFP reported.
Meeting with Secretary of State John Kerry at the State Department, coalition president Khaled Khoja thanked the United States for giving more than $3 billion in aid to the Syrian people since the outbreak of the war in 2011.
Speaking through a translator, he said he would brief Kerry on the latest political and military developments.
"We are here also to ask the assistance of the U.S. in establishing safe havens in liberated areas," Khoja was quoted as having said.
The moderate-opposition backed by the United States and its allies has been fighting to oust Syrian President Bashar Al-Assad, a battle Kerry admitted was against "difficult odds."
Successive attempts at launching peace talks have so far proved fruitless.
A key sticking point has remained Assad's future, with the National Coalition insisting he must step down, a demand refused by the government.
"President Assad has no legitimacy and he's not a part of the future of Syria and for that reason he needs to be prosecuted ... for the crimes he has committed against the Syrian people," Khoja insisted Thursday.
A delegation from the National Coalition will attend discussions in Geneva on Monday, when UN envoy to Syria Staffan de Mistura is to hold separate talks with the rival sides.
De Mistura is the third UN envoy to tackle Syria's conflict, which began in March 2011 with peaceful anti-government protests and descended into a war after a harsh regime crackdown.
He has already angered rebel groups by saying Assad was as "part of the solution" to the conflict in Syria. In response to those comments, rebels in Aleppo rejected de Mistura’s proposal for a temporary ceasefire in the city.
The situation in Syria "is simply unsustainable, catastrophic. It has profound impact... on each of the surrounding communities" with some three-quarters of the Syrian population now displaced, Kerry said Thursday, according to AFP.
Assad's regime "has lost all sense of any kind of responsibility," he said, adding there must be a transition "towards a government that represents all of the people and can repair this extraordinary damage."
Assad was "busy destroying the country in his own interests," Kerry said, adding that the Syrian leader was "enabling and attracting terrorists" such as the Islamic State which has seized control of a part of the country.
"We very much hope that in the immediate days ahead people will be able to find a new path... to restore the secular, united nature of Syria and be able to prevent this extraordinary humanitarian catastrophe."