The United States came "late" to an effort to end the Syrian civil war and is trying to prevent the total collapse of the country, Secretary of State John Kerry said on Monday.
"This is a very difficult process, which we come to late," Kerry said at a news conference, speaking of a U.S.-Russian effort to bring the warring parties to a peace conference in Geneva that might lead to a transitional government.
"We are trying to prevent the sectarian violence from dragging Syria down into a complete and total implosion where it has broken up into enclaves and the institutions of the state have been destroyed, with God knows how many additional refugees and how many innocent people killed," he added.
At least 80,000 people have lost their lives in the two-year uprising against Syrian President Bashar al-Assad, whose Alawite minority is an offshoot of Shi'ite Islam and whose family has ruled Syria for more than four decades.
Humanitarian groups say as many as 1,500 wounded people may be trapped in the besieged town Qusair by fighting between rebels and Assad's forces, who are backed by fighters from Lebanon's militant Shi'ite group, Hezbollah.
The peace conference that Kerry hopes to convene aims to implement an agreement hammered out 11 months ago, also in Geneva, that called for an end to the violence and the formation of a transitional government by "mutual consent."
Kerry said he and Russian Foreign Minister Sergei Lavrov had spoken on Friday and remained committed to trying to arrange the peace conference, known as Geneva II, but said whether it happens was up to the parties on the ground.
"Now when that ripens, when that becomes a reality, is going to be decided by events on the ground and the participants themselves," Kerry added at the news conference with Polish Foreign Minister Radek Sikorski.
"The Unites States can push and cajole ... but in the end, the people on the ground, are going to have to decide that that's something they are prepared to engage in," he added.