Russia and Iran have given fresh warning to the United States and its allies against a military intervention in Syria.
The Russian Foreign Ministry said on Tuesday that such an intervention could have "catastrophic consequences for the region and called on the international community to show "prudence" over the crisis.
"Attempts to bypass the Security Council, once again to create artificial groundless excuses for a military intervention in the region are fraught with new suffering in Syria and catastrophic consequences for other countries of the Middle East and North Africa," the ministry said.
Russia also expressed regret over a decision by the US to postpone a meeting scheduled for Wednesday in Hague in the Netherlands on an international peace conference for Syria.
Gennady Gatilov, Russia's deputy foreign minister, wrote on Twitter that such talks would have been particularly useful at a time "when military action is hanging over this country".
The US said the meeting had been postponed because of "ongoing consultations" over the alleged chemical weapons attack in Syria.
Separately, Iran repeated its opposition to any US attack by warning that a military intervention will engulf the whole region.
"There will definitely be perilous consequences for the region," Abbas Araqchi, Iranian Foreign Ministry spokesman, said.
In comments on Monday in Washington, John Kerry, the US secretary of state, signalled his country's intention to act on Syria, describing the use of chemical weapons as a "moral obscenity" and pinning the blame on President Bashar al-Assad government.
In a strongly worded and emotive statement on Monday, Kerry said that it was "undeniable" that chemical weapons killed hundreds of people near Damascus last Wednesday.
He said the Syrian government must be held accountable.
Kerry's statement came hours after a UN team visiting Syria was fired upon while they travelled to the attack site to begin investigations.
Al Jazeera's Patty Culhane, reporting from Washington, said President Barack Obama had not made any final decisions but it seemed clear from Kerry's comments that the US was putting itself in a position where it wouldl have to do something.
Obama is weighing a military strike against Syria that would be of limited scope and duration, the Washington Post reported on Tuesday.
Such an attack, which would probably last no more than two days and involve sea-launched cruise missiles - or, possibly, long-range bombers - striking military targets in Syria, the newspaper said.
Senior US administration officials told the Post that possible attack would be designed to serve as punishment for Syria’s use of chemical weapons and as a deterrent, while keeping the US out of deeper involvement in country’s civil war.
The British government has also said its armed forces were drawing up contingency plans for military action in Syria.
A spokesman for David Cameron, the British Prime Minister, told reporters on Tuesday that the UK government was considering a proportionate response to last week's alleged chemical weapons attack near the Syrian capital Damascus.
Cameron recalled the UK Parliament from summer break to discuss the latest developments on Syria on Thursday.