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The US has asked Russia to take part in a "true cessation of hostilities" in Syria, and warned it is running out of patience with its continued bombing of war-torn Aleppo.

The request came a day before peace talks in Geneva, following an opposition plan to end Syria's ongoing war.

US Secretary of State John Kerry will meet his Russian counterpart Sergey Lavrov in the Swiss city to push for a peace agreement.

The talks will focus "on reducing violence, expanding humanitarian assistance for the Syrian people, and moving toward a political solution" to end the nearly six-year war spokesman John Kirby said in a statement.

Meanwhile, US-backed forces continued to push the Islamic State group away from the Turkish border, while a suspected American air strike killed Syrian rebel leaders.

US Defence Secretary Ash Carter told BBC radio that there was "quite a long way to go" before a final peace deal could be struck but callef for "a true cessation of hostilities".

He said that the "partial cessation of hostilities" Russia had abided to does not go far enough.

"Our patience is not unlimited," he added.

Meanwhile, Turkish President Recep Tayyip Erdogan and Russian leader Vladimir Putin agreed to intensify efforts for a ceasefire "as soon as possible" in Aleppo, Anadolu reported.

Moscow has backed the Syrian regime with air raids on rebel groups, while Turkey is a keen backer of anti-Bashar al-Assad opposition forces.

Talks earlier in the day between Putin and US President Barack Obama in China failed to make headway.

Lavrov hinted that US sanctions on Russia over the country's involvement in the Ukraine war could be part of the reason for a lack of a breakthrough on Syria.

Carter noted, "We have our differences, serious differences, with Russia elsewhere, especially here in Europe with Ukraine."

Agencies contributed to this story.