Russian Foreign Minister Sergei Lavrov has said any attempt to enforce a no-fly zone over Syria using F-16 fighter jets and Patriot missiles from Jordan would violate international law.

The US has several thousands troops in Jordan on a joint military exercise.

"There have been leaks from Western media regarding the serious consideration to create a no-fly zone over Syria through the deployment of Patriot anti-aircraft missiles and F-16 jets in Jordan," said Mr Lavrov, speaking at a joint news conference with his Italian counterpart.

"You don't have to be a great expert to understand that this will violate international law."

His comments came after the leaders of Britain, France, Germany and the US held a video conference call to discuss the conflict in Syria.

David Cameron, Francois Hollande, Angela Merkel and Barack Obama spoke ahead of the G8 summit in Co Fermanagh next week.

They agreed on the need for a political transition in Syria, but not on how it should be brought about.

The US has said it was willing to provide military help to the Syrian opposition after stating it had conclusive evidence that President Bashar al-Assad's forces had used chemical weapons.

The Syrian government dismissed as "full of lies" the US claims that it used chemical weapons.

Mr Lavrov said the US plans to arm the rebels will not contribute to stabilising the situation in the region.

Mr Cameron said the British government's position is that no decision had been taken to arm moderate rebels opposed to Mr Assad.

However, he said that he was a "brutal dictator who is using chemical weapons under our nose".

The UN estimates that around 93,000 people have been killed in the two-year conflict.

Elsewhere, former British prime minister Tony Blair has said the West must intervene against the Syrian government's regime to prevent "catastrophic consequences".

In an interview with The Times newspaper, Mr Blair said he fears both sides of the conflict will begin to use chemical weapons as an "acceptable form of warfare" if no action is taken.

"I feel very strongly that we are in danger of a failure with catastrophic consequences," he told the newspaper.

"This is no longer a civil war between fractions within Syria. We should be taking a more interventionist line.

"You don't have to send in troops, but the international community should think about installing no-fly zones."