At the same time, America and its allies have sought to sift through the Syrian opposition to determine who its key leaders are and where their allegiances lie. On Thursday, Carney seemed to vouch for the majority of the rebels, saying only "fringe" elements were aligned with Islamist extremists.
"We recognize and have said that there are elements to the Syrian opposition that do not share the democratic ideals of the broad Syrian people, who are not necessarily friends of the United States," he said.
"Those elements appear to us to be fringe elements. They do not represent the opposition as a whole. But we need to be mindful of that," Carney said.
"We believe that those who support al Qaeda or al Qaeda in Iraq and other elements are fringe elements of the opposition; that the broad opposition aspires to meet the democratic desires of the Syrian people," he said.
Toner emphasized the communication the U.S. has engaged in with Assad's opponents in Syria. "We've been working all along with the Syrian opposition, trying to improve their cohesiveness, trying to help them come together more as a cohesive body," Toner said. "We have seen progress."
"There's still a ways to go here, but we need to foster the Syrian opposition so that when this transition does come there is an adequate, functioning opposition to help shepherd this change," he said.
Clinton, in Copenhagen, played down the prospects of an imminent breakthrough deal among Washington and other world powers.
"We're nowhere near putting together any kind of coalition other than to alleviate the suffering," she said.
"We have to peel away the regime's continued support within Syria while bolstering our assistance to the opposition and by isolating the regime diplomatically and economically," she said.
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