The U.N. peace envoy to Syria on Tuesday rejected suggestions that a proposed truce in the northern city of Aleppo would play into President Bashar al-Assad's hands, saying it was a stepping stone in a political process and vital to allowing in aid.
Staffan de Mistura has been meeting Syrian opposition groups inTurkey over the past few days to try to convince them of a U.N. plan for a "freeze in the fighting", a bid to get badly-needed humanitarian assistance into the divided city.
The opposition, as well as some diplomats and analysts, say the initiative is risky and that Aleppo could face the same fate as the central city of Homs, where government forces have largely regained control.
"It's not a ceasefire like in Homs ... They (the opposition) need to feel comfortable that this is a U.N. plan that has only one aim -- freeze the fighting, bring in the aid, stop this conflict. And starting from Aleppo," de Mistura told Reuters.
"We're looking at many conditions and many aspects in order to reassure everyone because everyone has a problem of trust," he said, adding that his deputy would be traveling to Damascus to try to win the support of Assad's government.
Aleppo has been split roughly in half between opposition groups in the east and government troops in the west, with the remaining civilians subjected to "barrel bombing" campaigns. Barrel bombs are steel drums full of shrapnel and explosives.
The presence of al Qaeda offshoot Nusra Front, which has fought both alongside and against other opposition groups, has complicated the picture further.
De Mistura declined to say whether he expected Nusra to sign up to the truce plan but said they would be making a "bad calculation" if they sought to disrupt it.
The Western-backed National Coalition for Syrian Revolutionary and Opposition Forces, which met de Mistura in Istanbul on Sunday, has said any truce plan needs to be part of a wider strategy involving Assad's removal from power.
"We all know the solution is not just a freeze. Freeze is a stepping stone. It's a building stone for a political process," de Mistura said, adding the fall of Aleppo would create an additional 400,000 refugees.
"Aleppo is iconic ... It's a mosaic of the cultures, of religions of not only Syria and the Middle East but of the whole world. If Aleppo falls, it would be tragic."