Russia has given warning that an attack on Syria risked causing an "outburst of terrorism" in the region at a time when the government of President Bashar al-Assad is still ready for talks to end the conflict.

It has cautioned that military strikes against Syria would create even more refugees.

"All the more, politicians share our estimation that a military solution will lead to an outburst of terrorism both in Syria and in neighbouring countries," Sergey Lavrov, Russia's foreign minister, said on Monday after talks with his Syrian counterpart Walid al-Muallem.

Lavrov said Russia "cannot not be worried by the fate of Russians living in Syria whose health and life might be put at risk".

"The possibility for a political solution remains," he said, emphasising that Muallem had assured him at the talks in Moscow that Syria was still "ready for peace talks".

Russia and the US agreed in May to organise a peace conference in the Swiss city of Geneva, bringing all sides to the negotiating table but it has not happened amid continued US-Russian tensions.

"We are truly ready to take part in the Geneva conference without preconditions," Muallem said.

He earlier thanked Russia for its support as Syria's prinicpal ally.

"We are also ready for dialogue with all political forces who favour re-establishing peace in our country," he said. But he warned that the position would change if military strikes took place.

Shortly after the Moscow press conference ended, John Kerry, the US secretary of state, said in London with his British counterpart William Hague in which they reiterated that Assad was responsible for the chemical weapons attack at the centre of the current crisis.

Kerry said Assad could resolve the impasse surrounding the attack simply by turning over "every single bit" of his weapons stock to the international community within a week.

But Kerry said he thinks Assad "isn't about to do that".

Kerry's rejoinder

Kerry was also asked on Monday about comments Assad made to US journalist Charlie Rose in which Assad said there was no conclusive evidence about who is to blame for the chemical weapons attack.

Asked about Assad's denial, Kerry said, "I just gave you real evidence. ... We know that his regime gave orders to prepare for a chemical attack. We know they deployed forces."

Kerry also said on Monday that the control of chemical weapons in Syria was limited to President Assad, his brother Maher and an unnamed general.

"But under any circumstances, the Assad regime is the Assad regime and the regime issues orders and we have high level regime [members] that have been caught giving these instructions and engaging in these preparations," he said.

Maher is commander of Syria's Republican Guard and an elite armoured division.