Top EU official urges respect for 'UN process' on Syria

Referring to chemical attacks in the outskirts of Damascus on 21 August, he added that "information from a wide variety of sources seems to indicate the Syrian regime is responsible for these attacks."

But he indicated world leaders should wait for a report by UN weapons inspectors in Syria before taking decisions.

He also said: "There is no military solution to the Syrian conflict. Only a political solution can end the terrible bloodshed."

Van Rompuy rejected the idea the EU has lost credibility in its approach to Syria.

France is the only EU state which says it is willing to take part in a military strike with the US. British MPs have blocked UK action, while Italy has said strikes need a UN mandate.

Van Rompuy noted the EU is trying to find common ground, however.

"All countries big and small have an internal debate on Syria. You may have to make a difference between those who want to participate and those who are preparing some kind of political position vis-a-vis eventual attacks," he said.

"The most important thing is how we react collectively on eventual decisions made by other countries. We will co-ordinate our positions in the coming hours," he added.

He also said the EU is ready "to help the recovery, rehabilitation and transition in Syria" after the war ends.

The G20 brings together the world's richest and most influential countries, including the US, China and Russia.

The St Petersburg event was supposed to discuss the global economy, but the civil war in Syria - which has created 2 million refugees - is likely to dominate talks.

Russian President Vladimir Putin said nothing on Syria in his opening speech on Thursday, talking instead about economic "risk zone[s]" and "global imbalances."

He indicated on Wednesday he "doesn't exclude" backing a UN resolution for military action, so long as there is clear proof that Syrian President Bashar al-Assad's government was behind the 21 August attack.

In the past two years, Russia has vetoed every draft UN Security Council (UNSC) resolution on Syria proposed by Western countries.

Meanwhile, China, also a UNSC veto power, spoke out against Syria intervention on Thursday.

"Military action would have a negative impact on the global economy, especially on oil prices - it will cause a hike in the oil price," Chinese deputy finance minister, Zhu Guangyao, told press.

But for his part, US President Barack Obama is refusing to back down.

He said in Stockholm on Wednesday: "The moral thing to do is not to stand by and do nothing."