Syria's splintered opposition coalition insisted Saturday it would not go to peace talks in Geneva unless pressure was brought to bear on Damascus to abide by the outcome.
"We have always said that we are fully committed to Geneva. But we are worried that if we go there the Assad regime is not serious about the implementation of Geneva," said coalition spokesman Khaled Saleh.
He was speaking as the opposition battling to topple Syrian President Bashar al-Assad met in Istanbul to decide whether to attend a peace conference that world powers want to hold in Geneva.
The meeting involving the main umbrella group, the National Coalition, and due to run into Sunday took place as rebels retook a strategic base in northern Syria.
The UN-Arab League envoy tasked with trying to quell the Syrian conflict, Lakhdar Brahimi, warned earlier this week that bitter rival camps in the opposition must forge a united front for the proposed peace talks, dubbed "Geneva 2".
World powers unsettled by the vicious, two-and-a-half year war in Syria have been pushing for the peace negotiations between the warring sides and Arab states to take place before the end of the year.
But the initiative has been stalled by the opposition's internal dissent -- robbing it of credibility internationally and in the eyes of the rebels it is meant to represent -- and its demand for the talks to call for Assad's ouster.
A key faction in the opposition coalition, the Syrian National Council, has baldly refused to take part, and has threatened to break from the grouping if some members go.
Foreign ministers from 11 Western and Arab nations holding a "Friends of Syria" meeting in Britain last month to pave the way for Geneva 2 agreed Assad should have no role in any future Syrian government.
But that failed to convince the opposition to commit to Geneva.
"In politics everything is possible."
And Assad's regime, which has international diplomatic protection from Russia, has warned it will not take part if the aim is to call for Assad to leave power.
Assad refuses to acknowledge that his army is fighting a revolt, preferring to label the rebels "terrorists" sponsored by Arab rivals.
The president has also opened the door to possibly standing for re-election in polls next year, to the fury of the opposition and the consternation of the United States.
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Assad trying 'to buy more time'
Russian Deputy Foreign Minister Mikhail Bogdanov said this week that some opposition members have accepted an offer of informal talks in Moscow to precede the Geneva conference.
Turkey's foreign ministry meanwhile said Syrian opposition was justified to have "hesitations" about Geneva 2, particularly over its format and Assad's future role.
Turkey, which borders Syria and has received a flood of more than 600,000 refugees from the conflict, has become a key opponent of Assad.
The opposition coalition's spokesman said of the proposed Geneva meeting: "Everyone knows that the Assad regime is going to try to buy more time.... and kill more Syrian civilians."
He added: "We want to go to Geneva but everyone has to be serious, not only the Assad regime but its allies. We want the Russians to apply real pressure on the Assad regime."
Saleh noted that recent Russian pressure had been instrumental in making Assad destroy his chemical weapon stocks.
Asked about when the opposition might declare whether or not it was going to the talks, the spokesman said the coalition "certainly hadn't received any invitation from the UN".
Saleh stressed the opposition's categorical rejection of Assad playing a role in any negotiated solution to the conflict.
"It has become obvious to anyone that there is no role for Assad if Geneva 2 is really to be applied, whether in the transitional period or after that."
Of the president's future, he added: "I can only say that he deserves a fair trial."
A monitoring group, the Syrian Observatory for Human Rights, said Saturday that Syrian rebels -- among them Al-Qaeda loyalists -- firing Grad rockets overnight regained control of a strategic base near Aleppo in fierce fighting that killed more than 50 people.
Much of the base, located near Aleppo's international airport, had been seized from rebels on Friday by Assad troops backed by Hezbollah fighters.