Key powerbrokers were scrambling yesterday over plans to speed up a political settlement in Syria, with UN envoy Staffan de Mistura joining a second day of talks after negotiations in Moscow.

A new round of peace talks backed by Russia, Iran and Turkey began in the Kazakh capital Astana on Thursday in an attempt to revive a hobbled peace process.

The second day of the talks coincides with the anniversary of a devastating and strategically crucial victory by Syrian forces in Aleppo, the country's second-largest city and once a rebel stronghold, after a blistering Russian-backed offensive.

The Kremlin is hoping to convert its game-changing military intervention in Syria into a political settlement on its terms, and wants to bring together regime officials and the opposition for a "peace congress" at the Black Sea resort of Sochi.

The Kremlin's chief negotiator Aleksandr Lavrentyev said Thursday that "quite a lot of time" at the talks had been spent on Moscow's proposal for a "Congress of National Dialogue", and the issue is likely to feature high on the agenda yesterday as well.

The plenary session was scheduled to begin at around 1000 GMT, the Kazakh foreign ministry said.

But while both Russian officials and Syrian President Bashar al-Assad have spoken enthusiastically of the plan, rebel delegates are wary and the UN has yet to endorse the plan.

De Mistura, who held talks with Russian Foreign Minister Sergei Lavrov and Defence Minister Sergei Shoigu in Moscow on Thursday, had said that negotiations over a political settlement should proceed "one step at a time".

He acknowledged that the most recent round of talks chaired by the UN in Geneva this month -- the eighth -- "was not a good meeting" as tensions between government and rebel delegations boiled over.