Up until now, Russia and China, two of Syria’s biggest allies, have refused to condemn President Assad’s regime and join in calls for Kofi Annan’s peace plan to be followed, despite the growing death toll in the country.

European Council President Herman Van Rompuy, European Commission President Jose Manuel Barroso and EU foreign policy chief Catherine Ashton are among those invited to Mr Putin’s lavish estate for talks, also covering issues involving Iran and trade.

Ahead of the summit, an EU official told Reuters: "We need to make sure that Russia is using fully its leverage in convincing the [Assad] regime to implement [the peace plan].

"The Russian side has certainly not been very helpful in finding solutions in terms of a political way out."

US Secretary of State Hilary Clinton has also added her voice to the mix, telling Russian foreign minister Sergei Lavrov that the focus in Syria must shift to political transition.

"Assad's departure does not have to be a precondition, but it should be an outcome so the people of Syria have a chance to express themselves,” she said.

Last week, around 108 people were found murdered in the city of Houla, 49 of whom were children. Mr Assad has denied that his forces had any involvement in the massacre, saying it was something not even “monsters” would partake in.

He has blamed rebels in Syria, and the apparent influence of “outside forces”.

Witnesses on the ground however have stated that the crimes were carried out by pro-government militia men, leading to the expulsion of Syrian diplomats in many countries around the world.