International media outlets report that some sources say that Syria would be divided into informal zones of regional power influence and Bashar al-Assad would remain president for at least a few years under an outline deal between Russia, Turkey and Iran.

Such a deal, which would allow regional autonomy within a federal structure controlled by Assad, is in its infancy, subject to change and would need the buy-in of Assad and the rebels and, eventually, the Gulf states and the United States, sources familiar with Russia's thinking say.

“There has been a move towards a compromise,” said Andrey Kortunov, director general of the Russian International Affairs Council, a think tank close to the Russian Foreign Ministry.

“A final deal will be hard, but stances have shifted.”

Assad's powers would be cut under a deal between the three nations, say several sources. Russia and Turkey would allow him to stay until the next presidential election when he would quit in favor of a less polarizing Alawite candidate.

Iran has yet to be persuaded of that, say the sources.  But either way Assad would eventually go, in a face-saving way, with guarantees for him and his family.

“A couple of names in the leadership have been mentioned (as potential successors),” said Kortunov, declining to name names.

If Russia gets its way, new peace talks between the Syrian government and the opposition will begin in mid-January in Astana, the capital of Kazakhstan, a close Russian ally.

Foreign and defense ministers from Russia, Turkey and Iran met in Moscow on December 20 and set out the principles they thought any Syria deal should adhere to.

Russian sources say the first step is to get a nationwide ceasefire and then to get talks underway.  The idea would then be to get Gulf states involved, then the United States, and at a later stage the European Union which would be asked, maybe with the Gulf states, to pick up the bill for rebuilding.

According to Reuters, Turkey's public position remains strongly anti-Assad however and Foreign Minister Mevlut Cavusoglu said on Wednesday a political transition with Assad was impossible.

Turkey reportedly wants to informally control a swathe of northern Syria giving it a safe zone to house refugees, a base for the anti-Assad opposition, and a bulwark against Kurdish influence.

Iran's interests are harder to discern, but Ali Akbar Velayati, Iran's Supreme Leader Ayatollah Ali Khamenei's top adviser, said Aleppo's fall might alter a lot in the region.

By helping Assad retake Aleppo, Tehran has secured a land corridor that connects Tehran to Beirut, allowing it to send arms to Hezbollah in Lebanon.

Russian and Western diplomatic sources say Iran would insist on keeping that corridor and on Assad staying in power for now.  If he did step down, Tehran would want him replaced with another Alawite, which it sees as the closest thing to Shia Islam.

Iran may be the biggest stumbling block to a wider deal.

Iranian Defense Minister Hossein Dehghan has said Saudi Arabia must not take part in talks because of its stance on Assad - Riyadh wants the Syrian leader to step down.