The United States defence secretary has indicated the US is moving naval forces into place in case President Barack Obama orders military action against Syria.
Chuck Hagel says Mr Obama has asked the Pentagon to provide a range of military options.
Mr Obama says the alleged attack, which rebels say killed between 500 and 1000 civilians, is of grave concern.
He says it affects America's core interests and requires the United States attention.
However, Mr Obama stressed during a CNN interview that he was in no rush to embroil Americans in a costly new war.
Early intelligence points to chemical weapons in Syria
American and allied intelligence agencies have made a preliminary assessment that Syrian forces used chemical weapons to attack an area near Damascus this week.
They also believe the act is likely to have had high-level approval from President Bashar al-Assad's government.
United States security sources, speaking on condition of anonymity, cautioned that the assessment is preliminary and, at this stage, they are still seeking conclusive proof, which could take weeks or longer to gather, Reuters reports.
Moscow has urged Mr al-Assad to cooperate with a United Nations investigation into the incident.
A statement on the Russian foreign ministry website accuses the Syrian opposition of preventing an objective investigation.
The ministry says it believes the rocket involved in the attack was fired from rebel-held territory.
In Australia meanwhile, AAP reports that Prime Minister Kevin Rudd has called a temporary halt to his election campaign for urgent intelligence briefings about the situation in Syria.
He has the full support of Opposition Leader Tony Abbott who dismissed a suggestion that Mr Rudd's sudden return to Canberra might be a political stunt.
