Major powers agreed on Friday to a cessation of hostilities in Syria set to begin in a week and to provide rapid humanitarian access to besieged Syrian towns, but failed to secure a complete ceasefire or an end to Russian bombing.

Following marathon talks in Munich, the powers, including the United States, Russia and more than a dozen other nations, reaffirmed their commitment to a political transition when conditions on the ground improved.

But diplomats cautioned that Russia had until now not demonstrated any interest in seeing President Bashar al-Assad replaced and was pushing for a military victory.

At a news conference, U.S. Secretary of State John Kerry acknowledged the Munich meeting produced commitments on paper only.

‘What we need to see in the next few days are actions on the ground, in the field,’ he said, adding that ‘without a political transition, it is not possible to achieve peace.’

Kerry said the cessation of hostilities would not apply to Islamic State and other militant groups fighting in Syria, he added. Islamic State militants control large parts of Syria and Iraq.

Russian Foreign Minister Sergei Lavrov told the news conference that Russia would not stop air attacks in Syria, saying the cessation of hostilities did not apply to Islamic State and al Nusrah, which is affiliated with al Qaeda.

‘Our airspace forces will continue working against these organizations,’ he said.

The United States and European allies say few Russian strikes have targeted those groups, with the vast majority hitting Western-backed opposition groups.

Lavrov said peace talks should resume in Geneva as soon as possible and that all Syrian opposition groups should participate. He added that halting hostilities would be a difficult task.

But British Foreign Secretary Philip Hammond said ending fighting could only succeed if Russia stopped air strikes supporting Syrian government forces' advance against the opposition.

Opposition group cautious

Syria's main opposition group welcomed the plan.

It cautioned, however, that the agreement must prove to be effective before it joins political talks with government representatives in Geneva.

The Assad government for years has repeatedly promised humanitarian access but has rarely lived up to its promises. Western-backed rebels have also been accused of that.

Russian Prime Minister Dmitry Medvedev on Thursday raised the spectre of an interminable conflict or even a world war if powers failed to negotiate an end to the fighting in Syria, which has killed 250,000 people, caused a refugee crisis and empowered Islamic State militants.

The first peace talks in two years between belligerents in Syria collapsed last week before they began in the face and the offensive by Assad's forces against opposition forces, one of the biggest and most consequential of the five-year war.

A senior French diplomat said: ‘The Russians said they will continue bombing the terrorists. They are taking a political risk because they are accepting a negotiation in which they are committing to a cessation of hostilities. If in a week there is no change because of their bombing, then they will bear the responsibility.’