By Dasha Afanasieva
ISTANBUL (Reuters) - Syria's Western-backed opposition agreed on Monday to attend planned peace talks in Geneva but said President Bashar al-Assad could play no part in a transitional government aimed at ending the 2-1/2-year-old civil war.
The Syrian National Coalition also demanded the release of women and children from Syrian jails and an easing of military sieges of rebel-held areas as a precondition for going to Geneva.
No date has yet been agreed for the peace talks, which have been repeatedly delayed by discord between Washington and Moscow and by the coalition's failure to define its stance until now.
"The coalition agreed to take part in the conference on the basis of a transfer of power to a transitional ruling authority with full powers, including the presidency, military and security," it said in a statement after late-night talks.
There could be no role for Assad "or his aides whose hands are stained with Syrian blood" in Syria's future, it said.
The United States welcomed the coalition's decision to attend the talks and endorsed its conditions relating to prisoner releases and humanitarian access.
"We will continue to work closely with our international partners, including Russia, to urge the regime to take these steps and move towards convening the Geneva conference," a State Department spokesman said, without commenting on the coalition's rejection of any role for Assad in any interim government.
The United States and its Western and Arab allies, which have all called on Assad to step down, say last year's Geneva agreement ruled out a future role for the president. Russia, Iran and other supporters of Assad challenge that view.
Syrian National Coalition leader Ahmad Jarba had expressed willingness to attend the U.S- and Russian-sponsored talks but this was the first time the whole group had backed the idea.
"BLOOD ON THEIR HANDS"
"Our position makes it clear that Geneva must result in the removal of Assad, and that Assad and his cohorts with blood on their hands have no role in any transition," coalition vice-president Farouq Tayfour told Reuters in Istanbul.
"Foreign forces must also leave the country," he said, without specifying which forces. Sunni Muslim jihadis have flocked to Syria to fight Assad's army, while the president has been supported by Shi'ite Iran and Hezbollah fighters.
Tayfour said last-minute touches were being made to the coalition declaration, but several delegates said they did not expect significant changes to the position on the Geneva talks.
Assad himself, after months of steady gains on the battlefield, has given no suggestion that he is ready to step down and his ministers have repeatedly said that the government would not show up in Geneva simply to surrender power.
He has also refused to talk to rebels viewed by Damascus as terrorists and said no one who backs foreign political or military intervention in Syria can sit at the negotiating table.
The coalition's envoy in France, Monzer Makhous, said almost everyone had voted for the statement, which addresses demands made by fighters on the ground. "We know very well that they should be a part of any (peace) project," he told Reuters.
The statement said the coalition would hold talks with rebels in Syria, many of whom openly despise the politicians in exile and say they represent the interest of foreign powers.
A group of leading rebel brigades said two weeks ago they would charge with treason anyone who attended peace talks which did not result in an end to Assad's rule.
A rebel who uses the name Abu Nidal, from the Mustafa Brigades in Damascus, said on Monday that his group rejected the Geneva meeting, saying it "does not meet our aspirations".
The coalition statement said the Geneva talks should be based an international accord agreed in the Swiss city on June 30, 2012, which endorsed the idea of a transitional government.
The statement did not refer directly to another disagreement among international powers - whether Iran should attend.
The Syrian National Coalition reached the consensus decision after two days of discussions. In further talks on Monday, the coalition was expected to approve a cabinet led by Ahmed Tumeh and charged with restoring order in rebel-held areas.
(Additional reporting by Khaled Yacoub Oweis in Amman and Oliver Holmes in Beirut; editing by Dominic Evans and Alistair Lyon)