Heads of international powers have agreed to a ceasefire in Syria within a week, US Secretary of State John Kerry said.

The 17 countries meeting in Munich who were holding crisis talks agreed “to implement a nationwide cessation of hostilities to begin in a target of one week’s time” and immediately expand delivery of humanitarian aid, he said.

“We have agreed to accelerate and expand the delivery of humanitarian aid beginning immediately,” Mr Kerry said.

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“Sustained delivery will begin this week, first to the areas where it is most urgently needed … and then to all the people in need throughout the country, particularly in the besieged and hard to reach areas.”

Mr Kerry said, however, this would not apply to jihadist groups Islamic State (IS) or al-Nusra Front.

He also said international powers had agreed to expand and accelerate the delivery of aid, according to the BBC.

Speaking after marathon talks that included Russia and more than a dozen other countries, Mr Kerry said that all nations involved in the talks agreed that Syrian peace negotiations should resume in Geneva as soon as possible.

Syria has been decimated by a war between President Bashar al-Assad, rebel anti-government forces and the notorious IS.

The US, Australia and other western forces had been supporting the anti-government forces, while Russia had been fighting with Assad.

– with ABC