Foreign ministers from 11 Western and Arab countries on Tuesday urged the moderate Syrian opposition to unite and attend planned peace talks in Geneva next month, with the US warning that it was "imperative" for both sides to negotiate, dpa reported.
"This war will not come to an end on the battlefield," US Secretary of State John Kerry told reporters after meeting his Friends of Syria counterparts in London. "It is imperative that we try to get to the negotiating table."
The main opposition grouping, the National Coalition led by Ahmed al-Jarba who also attended the talks, is to decide in the coming weeks whether it will attend the Geneva conference.
A prominent group in the coalition, the Syrian National Council, has said that Geneva cannot go ahead while Syrians continue to suffer under the regime of President Bashar al-Assad.
Kerry warned that a failure to end the conflict would lead to the rise of extremism, more refugees and the further destabilization of the region which would "ultimately lead to the disintegration of the Syrian state."
He also denied reports of a rift between the United States and Saudi Arabia, which was disappointed over the US' failure to carry out military strikes against the Syrian regime.
He had spent a "delightful and constructive" few hours with the country's Foreign Minister Saud al-Faisal in Paris on Monday, said Kerry, adding that they were "on the same page."
The foreign ministers from France, Germany, Italy, Turkey, Egypt, Qatar, and the United Arab Emirates made up the rest of the 11 who attended the meeting.
Host British Foreign Minister William Hague underlined that al-Assad could play no part in the transitional government, to which it is hoped the Geneva conference could lead.
The Geneva process "must lead to the establishing by mutual consent of a transitional governing body," he said.
"By definition mutual consent means that it can only be agreed with the consent of the Syrian National Coalition, so (Syrian President Bashar) Assad would play no role in the future government of Syria," he said.
In a final communique, the grouping promised to "step up" its support for the moderate opposition and demanded full humanitarian access for aid workers.
Al-Assad has already confirmed that he will send a delegation to Geneva, and in an interview with the Lebanese pro-Syrian al-Mayadeen television channel late Monday, said he saw "no obstacles" to his running for power again in 2014.
He also reiterated accusations that Turkey, Qatar and Saudi Arabia were "sending terrorists to fight inside Syria."
It is not yet clear when the Geneva conference will take place.
At the weekend, Arab League head Nabil al-Arabi said it had been set for November 23 but at the same news conference UN-Arab League envoy on Syria, Lakhdar Brahimi, said the date had not been confirmed.
Also on Tuesday Sigrid Kaag, the special coordinator of the joint mission to dismantle Syria's chemical weapons said that Syria had "fully cooperated" with her team.
"The timeframes are challenging given the goal of the elimination of Syria's chemical weapons programme in the first half of 2014," added Kaag, who arrived in Damascus on Monday.
A team of inspectors from the United Nations and the Organisation for the Prohibition of Chemical Weapons arrived in Syria on October 1 to oversee the implementation of a Security Council resolution, which orders the destruction of Syria's chemical weapons and production facilities by mid-2014.
The uprising that started against the regime of al-Assad in March 2011 has caused more than 100,000 deaths, according to UN estimates.