AFP/Moscow

Russia said Saturday it was ready to provide air support for Western-backed moderate rebels battling both jihadists and Syrian President Bashar al-Assad as Moscow presses on with its diplomatic offensive over the conflict.

Speaking after a surprise summit between Syria's embattled leader and Russian President Vladimir Putin at the Kremlin this week, Foreign Minister Sergei Lavrov urged moves towards presidential and parliamentary polls in the war-torn country.

Representatives of Syria's Western-backed opposition sounded incredulous, saying Russia should first stop bombing moderate rebels and that talk of elections was premature.

On the ground, Syrian troops backed by Russian air strikes battled fighters from the Islamic State (IS) group in a bid to restore a key supply line to second city Aleppo, the Syrian Observatory for Human Rights said.

At least 28 IS fighters and 21 troops and pro-regime militia have been killed in the battle for the road leading to the government-held part of Aleppo, it said.

The monitors also reported Russian strikes in northern Hama province and said six people were killed, including three children.

Russia and the West have been at loggerheads over Assad's fate, a major sticking point in efforts to solve a crisis that has killed more than 250,000 people since 2011 and sparked an exodus of around four million refugees.

Seeking to shake off months of Western isolation over the Ukraine conflict, Putin last month launched air strikes in Syria and has since launched negotiations with the war's key regional players, including some of Assad's worst enemies, such as Saudi Arabia and Turkey.

But Washington has accused Moscow of seeking to buttress Assad by bombing moderate rebels in Syria, and refused to share intelligence over Syria.

 A shift in Russia's position?

 Analysts say Lavrov's offer of support for the anti-Assad opposition in the fight against IS could point to a shift in the Kremlin's position.

"We are ready to also support patriotic opposition, including the so-called Free Syrian Army, from the air," Lavrov said in an interview with the Rossiya 1 television channel. 

Russia has previously only used the words "patriotic" or "healthy" to describe groups backing Assad.

Moscow says it has struggled to identify areas controlled by moderate rebels and has urged the West to help build bridges.

The Russian government released the transcript of the interview after Lavrov and US Secretary of State John Kerry agreed in Vienna on Friday to explore new ways of trying to reach a political settlement.

Lavrov, who spoke to Kerry again on Saturday, also said the huge influx of migrants to Europe -- many of them Syrian refugees -- had helped shift EU politicians' thinking, which could potentially lead the way to fresh talks on Syria's future.

"Of course, it's necessary to prepare for both parliamentary and presidential polls," Lavrov added.

 'We don't understand Russia'

 Western-backed Syrian rebels rejected Russia's offer of help under current circumstances.

"Russia is bombing the Free Syrian Army and now it wants to cooperate with us, while it remains committed to Assad?" said Lieutenant Colonel Ahmad Saoud, a spokesman for the Division 13 rebel group.

"We don't understand Russia at all!"

But things could be different if Assad quits power, he suggested.

"In the event that Assad leaves, there is a transitional government, a ceasefire and the formation of a national army to serve its country, we will try to forget the pain in order to build our country."

Samir Nashar, a member of the Syrian National Coalition, the opposition's main political body, said the proposal of new elections was absurd and accused Moscow of trying "to circumvent the demands of the Syrian people for Assad's departure".

Syria last held presidential elections in June 2014, with Assad re-elected for a seven-year term with 88.7 percent of the vote.

The election was dismissed by the opposition and condemned internationally.

 'Things resolve themselves'

 Some analysts say Moscow may not be married to the idea of Assad staying in power indefinitely, with others suggesting the Kremlin may be nudging the disgraced leader to share power.

Jeremy Binnie, Middle East editor at IHS Jane's Defence Weekly, said Putin wants to see a settlement in Syria and is "prepared to retire Bashar al-Assad to achieve that goal".

Washington and its allies say there is no role for Assad in the future, although some of them have said recently his resignation need not be immediate.

Putin has stressed that Assad's fate should be decided by the people and said Russia's possible support for the moderate rebels was agreed with the Syrian leader.

In a sign of progress, Russia and Jordan, a member of a US-lead coalition that is also bombing IS targets, agreed to "coordinate" their air operations in Syria. 

Kerry welcomed the deal and said he was not worried by the absence of a common position on Assad's fate.

"If we can get into a political process, sometimes these things have a way of resolving themselves."