The Syrian National Coalition opposition group will attend the long-delayed "Geneva 2" talks in January aimed at ending the country's civil war, the group's president, Ahmad Jarba, said on Wednesday.
In an interview with Reuters and the Associated Press, he also said regional power Iran should only be allowed to attend if it stopped taking part in the bloodshed in Syria and withdrew its forces and proxies.
The coalition said previously it was ready to attend if humanitarian aid corridors were set up and political prisoners released. It insists that President Bashar al-Assad can play no future role in Syria.
"We are now ready to go to Geneva," Jarba said on a visit to Cairo, adding that the opposition viewed the Geneva talks as a step to a leadership transition and a "genuine democratic transformation in Syria".
"There is no way that the individual responsible for the destruction of the country can be responsible for building the country," said Jarba, referring to Assad.
Assad has consolidated his power around Damascus and central Syria after months of steady military gains. With support from Iran and Russia and backed by fighters from Lebanon and Iraq, his soldiers recaptured towns this month on the edge of the capital and the southern approaches to Aleppo.
More secure than a year ago from the mainly Sunni rebels, whose ranks are also swelled from abroad by an influx of Islamist jihadi fighters, Assad faces little internal pressure to make concessions to his enemies.
Syria said on Wednesday that Western countries that also demand that Assad step down should either stop "dreaming" or forget attending the peace talks.
Jarba rejected the idea of Iran taking part "under the current reality".
"Iran is responsible for and takes part in the killing in Syria in a very clear way. It killed thousands of Syrians with its Revolutionary Guards and mercenaries from Hezbollah, which is considered a terrorist group," he said.
"If Iran is serious about resolving the Syrian crisis, it must first withdraw its Revolutionary Guards and (Lebanese) Hizbollah mercenaries."
IRAN CALLS FOR CEASEFIRE
Iran is the main backer, along with Russia, of Assad during a conflict that has lasted more than two years, killed more than 100,000 people and uprooted millions more.
Tehran has said it would attend Geneva 2 if invited and called on Wednesday for a ceasefire before the talks scheduled for January 22.
Western diplomats say Iran provides billions of dollars of aid and an undisclosed number of military advisers to Syria.
Lebanon's Iranian-backed Hezbollah group openly acknowledges its guerrillas are fighting for Assad, but Tehran denies its troops have been engaged directly in combat in Syria.
"Iran is a participant in the killing of the Syrian people," said Jarba, who is backed by Sunni power Saudi Arabia, Shi'ite Iran's rival.
"If it wants to attend (Geneva talks), it is obliged to withdraw its forces and Hezbollah forces and Iraqi forces allied to it."
Asked what kind of weapons Saudi Arabia was providing for the opposition, Jarba said: "We often asked the international community and the Western world and Arab world for weapons. This is something we welcome."
The head of the Western-backed Free Syrian Army rebel brigades has rejected the Geneva talks and says there will be no ceasefire during the meeting.
Powerful Islamist fighters have gone further, threatening to put on trial anyone who attends talks that do not deliver Assad's ouster.