US officials were working hard behind the scenes Wednesday to try to persuade the Syrian opposition to agree to join peace talks mooted for next month.
US ambassador to Syria Robert Ford, who has built up a close relationship with the opposition leaders over the past years, huddled with key figures in Istanbul seeking to coax them to the negotiating table.
"Ambassador Ford is in Istanbul as we speak having meetings with the opposition to help continue to get them to increasingly coalesce," deputy State Department spokeswoman Marie Harf told reporters.
Prospects for peace negotiations, which have been in works since May, dimmed again Wednesday as leaders of the National Coalition -- the main opposition umbrella group -- insisted they would not attend the talks slated to be held in Geneva in late November.
"Their participation is pivotal. We will continue encouraging them to attend, and that's why Ambassador Ford's on the ground talking to them right now in Istanbul," Harf said.
But the opposition is refusing to sit at the same table as members of the Syrian regime.
"The only thing we are willing to negotiate is a transfer of all power and then the departure of the mass killer," said coalition head Ahmad Jarba said, referring to Syrian President Bashar al-Assad.
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He also reiterated a call for the rebels' supporters, including the US, to open up humanitarian corridors to reach civilians under siege in Damascus and the Syrian city of Homs.
"We cannot sit at the negotiating table while, in some areas, children are dying of hunger and women are being tortured in jails," Jarba said.
The aim of the peace negotiations -- dubbed Geneva II -- is to map out a path towards a transitional government in Syria and hopefully end the fighting which has left an estimated 115,000 people dead since it erupted in March 2011.
Prior to the planned late November talks, Ford and US Undersecretary of State Wendy Sherman will meet in Geneva on November 5 with Russian officials and UN-Arab League special envoy to Syria, Lakhdar Brahimi, to try to plot a way forward.
"This is a chance -- another meeting to have a trilateral dialogue to review progress towards a Geneva II conference and hopefully work out some of the issues that we need to work out before then," Harf said.
She said it was possible that the United Nations might announce the date of the conference -- dubbed Geneva II -- after the November 5 talks.
"We don't have official dates yet... But we're still tracking towards late November," Harf said.
A defiant Assad has shown no sign of backing down after a two-and-a-half-year civil war, and on Monday he too poured cold water on the plans for a peace conference, saying the right factors were not in place for it to succeed.