Bolstering Syria’s moderate opposition is crucial to excluding extremists from power in the war-gripped country, the UK’s foreign secretary has said.
William Hague was speaking as Arab and Western foreign ministers gathered for talks with Syrian opposition officials.
The London talks are trying to lay the groundwork for planned peace negotiations in Geneva next month.
But a key group in Syria’s main opposition alliance is threatening to boycott the meeting dubbed Geneva II.
The Syrian National Council (SNC) has been unwilling to talk to representatives of Bashar al-Assad’s government.
Ministers will say unity is vital among the fractured groups of Syria’s armed and political opposition if peace talks are to have any chance of success.
In London, foreign ministers from 11 countries – the so-called Friends of Syria group – are trying to encourage opposition groups “to have a united position” ahead of Geneva II, Mr Hague told the BBC’s Today programme.
“I don’t see any obstacles to being nominated to run in the next presidential elections”
Bashar al-Assad, Syrian President
Mr Hague admitted that an increasingly prominent role was being played in Syria by Islamist rebels linked to al-Qaeda, who are engaged in no kind of peace process and who have been involved in bitter struggles with more moderate forces.
“The reason we have to make sure we are supporting and dealing with the moderate opposition committed to a democratic, pluralistic, non-sectarian future for Syria is precisely because if they don’t have a role, then all the Syrian people have got left is a choice between Assad and extremists,” Mr Hague said.
“The longer this conflict goes on, the more sectarian it becomes. That’s why we’re making a renewed effort” with Geneva II, Mr Hague said.
At Tuesday’s talks, Britain, Egypt, France, Germany, Jordan, Italy, Qatar, Saudi Arabia, Turkey, the United Arab Emirates and the United States are expected to reaffirm their view that Geneva II must be about a political transition in Syria away from the Assad regime.
The BBC’s Lina Sinjab reports on the different warring factions in Syria
Iran as yet has no role in Geneva II, but Mr Hague said he was trying to use new positive diplomatic relations with Iran to encourage it to play a “more constructive role” – but that required Iran to back a “transitional government in Syria made up of regime and opposition, by mutual consent”.
Earlier, the US Secretary of State John Kerry stressed that Syria’s opposition would never agree to President Assad staying in power.
“He has bombed and gassed people in his country. How can that man claim to rule under any legitimacy in the future?” he said, dismissing suggestions that Mr Assad could stand for re-election in 2014.
But President Assad reportedly told Lebanon’s al-Mayadeen television that he saw no reason why he could not run.
“Personally, I don’t see any obstacles to being nominated to run in the next presidential elections,” he was quoted as saying by the channel.
Mr Assad told the channel that his government would take part in the conference without preconditions, but suggested the prospects that it would reach a settlement were, at present, dim.
“No time has been set, and the factors are not yet in place if we want to succeed,” he told al-Mayadeen in comments reported by AFP news agency.
“Which forces are taking part? What relation do these forces have with the Syrian people? Do these forces represent the Syrian people, or do they represent the states that invented them?” he asked.
Saudi Arabia and Qatar are key funders of opposition forces in Syria, including, it is believed, hardline Islamist groups.
On Monday, the main opposition alliance, the National Coalition, said it was postponing until early November meetings to decide whether to attend the Geneva II conference.
The opposition has been further weakened by fighting between the moderate Free Syrian Army and Islamist rebel groups.
Western officials have been buoyed by the initial results of the chemical disarmament effort in Syria, the BBC’s diplomatic correspondent Jonathan Marcus says.
But he adds that they are painfully aware that the recent chemical deal has done nothing to alter the course of the civil war or to reduce the burgeoning humanitarian catastrophe in and around Syria.
Participants at the first round of talks in June 2012 (Geneva I) had sought to end the civil war by getting Damascus and the opposition to choose a transitional government.
The National Coalition has insisted that President Assad play no role in a transitional authority – something the Syrian government has rejected.
More than 100,000 people have been killed since the Syrian conflict began in 2011.