PM calls for pragmatic Syria solution

Malcolm Turnbull has backed a power-sharing deal in Syria as he dismissed boots on the ground as counterproductive.

The prime minister said only a political solution inclusive of all the various groups in the war-ravaged country could defeat Islamic State by cutting away the extremists' support base there.

A day after holding talks with Barack Obama, the prime minister said the US president felt that while he could send 50,000 marines into Syria and Iraq and succeed, the future beyond that was uncertain.

"His view is that - and this is the view of all the country leaders with whom I spoke - the presence of foreign armies in that theatre at the present time would be counterproductive given the lessons of recent history," Mr Turnbull told reporters in Manila on Wednesday.

The prime minister said most leaders agreed a Syria settlement would be undertaken in a "spirit of compromise" and that any foreign nations imposing their solution would be unsuccessful.

He said a pragmatic response was needed as quickly as possible.

"There needs to be a ceasefire ... and there needs to be a power-sharing deal."

Mr Turnbull said he spoke "at length" with Russian President Vladimir Putin on the sidelines of the G20 summit on Syria.

The Russian leader agreed a political settlement was also necessary.

"He has a view of how that can be achieved ... but the challenge is reaching agreement."

Meanwhile, Mr Obama has praised Russia's role in talks to end the Syria crisis and offered the prospect of better ties if Moscow focused military strikes on IS.

But he said there were still differences over the fate of Syrian ruler Bashar al-Assad, and Moscow's current military focus on defending him.

"There is obviously a catch, which is Moscow is still interested in keeping Assad in power," Mr Obama said.

"Those differences have not prevented us looking at how could we set up a ceasefire."