U.S. Secretary of State John Kerry and the U.N.-Arab League envoy for Syria say an international conference to set up a Syrian transitional government must be organized urgently and held as soon as possible.
After talks Monday in London with Lakhdar Brahimi, Kerry said that Syrian President Bashar al-Assad "has lost the legitimacy to be a cohesive force that could bring people together." He also called for a new government in Syria.
"It is clear that in implementing Geneva One, which is the only purpose for having a Geneva conference now, that there has to be a transition government. There has to be a new governing entity in Syria in order to permit the possibility of peace."
Kerry said it was imperative to get the so-called "Geneva II" conference organized by a mid-November target the United Nations has set.
Brahimi agreed, saying a precise date for the peace talks must be set "very soon."
A key opposition group, the Syrian National Council, said Sunday it would not take part and criticized the international community's response to the fighting.
Meanwhile, aid officials said a Syrian Arab Red Crescent volunteer and three of six Red Cross staffers abducted in Syria are free and safe.
A spokesman for the International Committee of the Red Cross said the four were released in the Idlib region, but gave no details on their identities or circumstances of their liberation. He said the ICRC was awaiting information on the remaining three.
Unidentified gunmen seized the aid workers in northwest Syria on Sunday as they were returning to Damascus after a four-day mission to deliver medical supplies in Idlib.
Kidnappings have become increasingly common in northern Syria, where rebel factions fighting the Syrian government have captured large areas.
Also Monday, activists said a car bomb exploded in the northern town of Darkoush near the Turkish border, killing at least 20 people and wounding dozens of others. The Syrian Observatory for Human Rights said the blast hit the town's market. There has been no claim of responsibility for the blast.