Ahmed Moaz al-Khatib published his initiative on Facebook, as the main National Coalition he headed until March gathered in Istanbul to choose a new leader and discuss a US-Russian peace initiative dubbed Geneva 2.

Under Khatib’s initiative, Assad would have 20 days from Thursday to give “his acceptance of a peaceful transition of authority”.

After accepting, Assad would have one month to hand over power to either Prime Minister Wael al-Halqi or Vice President Faruq al-Sharaa, who would then govern Syria for a transitional period of 100 days.

As part of the transition Khatib envisages, Assad would “leave the country along with five hundred people whom he will select, along with their families and children, to any other country that may choose to host them”.

This is the first time one of Syria’s opposition chiefs has made an offer of political immunity to Assad and key members of his regime.

Khatib’s proposal is an effort to pull Syria “out from the catastrophe that has struck our nation”, said the former Omayyad mosque imam and controversial opposition figure on Facebook.

It is also “a practical response to the need of a political settlement ensuring a peaceful transition of authority”, Khatib added.

“This initiative is a product of Syria and its goal is Syria,” he said.

While calling on dissident groups to adopt the initiative “as a way out from the catastrophe that has struck our nation”, Khatib also said the international community should “oversee it and ensure that it is implemented”.

This would be accompanied by the release of all political prisoners in Syria, Khatib wrote.

The initiative gives Assad a month to “completely hand over authority”, and stipulates that while parliament should be dissolved, all of its powers should be handed to Assad’s replacement.

Over the same 100-day period, an interim government would “restructure the security and military” apparatus in Syria, said Khatib.

He also suggested that the UN should appoint an international mediator to oversee the transition.

At the end of the 100 days, the responsibilities of the current government would pass to the transitional government, formed with international guarantees, which would “be responsible for the preparation and the re-building of the new Syria,” Khatib said.

Khaled Saleh, spokesman for the opposition coalition, said it was a “personal initiative” that would be “submitted at the coalition meeting and maybe discussed”.

“There have to be two, credible delegations to negotiate,” Eliasson told reporters in Geneva, the planned venue of the talks.

“We’re working very hard for a meeting as soon as possible. We’re in contact with the parties, and with the Security Council members, that are involved. But we hope very much that the meeting will take place, and soon,” he said.

Amid growing speculation that the talks could be held from June 10, Eliasson declined to be drawn on potential dates but confirmed that the target was still next month.

“It’s being worked out progressively now with the parties and we will have to wait for those consultations before we can conclude exactly how the conference will take place,” he said.

Last Friday, UN chief Ban Ki-moon and Russia agreed that a peace conference should be held as soon as possible, even as Security Council member Moscow defied growing global pressure over its arms supplies to the Damascus regime.

The talks are meant to include both the fiercest rebels and members of the regime — a problem given some opposition members’ refusal to recognize President Bashar Assad as a negotiating partner.

The main aim, Eliasson underlined, is to try to implement a peace plan drawn up on June 30 last year at a Geneva conference involving Western powers, Russia and China, Turkey, and the Arab League.

That plan’s measures include a ceasefire and a shift to a transitional government in Syria.

US President Barack Obama said last week that he will continue to press for Assad to leave power even if this is no longer a precondition of the Geneva talks.

The goal of holding talks was agreed during a May 7 visit to Moscow by US Secretary of State John Kerry.

Despite bitter splits over Syria, it is seen as a joint peace push by the two Cold War-era rivals, 26 months into the bloody Syria conflict which has claimed over 90,000 lives.

“The situation is desperate,” UNICEF spokeswoman Marixie Mercado told reporters in Geneva.

Her comments came as the battle for Qusayr, in central Homs province, raged for a third day after President Bashar Assad’s forces and allies launched an offensive to reclaim the town more than a year after rebels seized it.

UNICEF believes that between 12,000 and 20,000 civilians remain trapped in the town that used to count some 30,000 inhabitants, Mercado said.

“What are the most urgent needs? Protection,” she said, pointing out that those who remain “need to be protected from the bombardment, from the fighting that’s going on in the city right now.”

Mercado said that most of the civilians stuck in Qusayr were believed to be women and children, as were those who had managed to flee.

She said it remained unclear where the men who used to live in the city were.

UNICEF did not have any staff in the city, but was along with other organizations helping around “500 families made up of women, children and elderly” who had fled from Qusayr and nearby villages in recent days to Hasiaa, near Homs.

“They are joining an additional 1,144 families who had previously fled Qusayr, where fighting has flared over the past month,” she said, pointing out that for those who have left the city, there were also “just enormous needs right now.”

“Many of the families left at night with little or no possessions,” she said, adding that UNICEF and others were providing them with clothing, water and sanitation.

The Syrian Observatory for Human Rights, a Britain-based watchdog, has said some 25,000 civilians were still trapped in Qusayr, and described the rebel response to the assault on the city as “fierce.”

According to the Observatory, Hezbollah fighters from neighboring Lebanon are leading the attacks on the ground while Assad’s warplanes carry out air strikes.

Assad and Hezbollah have made reclaiming Qusayr, which lies between the Syrian city of Homs and Tripoli in northern Lebanon, a priority in its fight to turn the tide against the two-year insurgency.