President Barack Obama met with top US military and security advisers on Saturday to devise options over a potential US response to claims that chemical weapons were used in Syria amid "increasing signs" that troops loyal to Syrian President Bashar Assad used poisonous nerve gas against civilians .
Following his meeting in Washington, Obama called UK Prime Minister David Cameron, one of the US' strongest allies, and agreed that the use of chemical weapons by Assad and his loyalists would merit "a serious response", a spokeswoman for Cameron said in a statement, according to Reuters.
Syrian opposition forces claim that between 500 and over 1,000 civilians were killed on Wednesday when Syrian troops fired nerve gas towards the residential Damascus suburb of Ghouta.
The attack, which allegedly struck the civilians before dawn, has stoked demands abroad for a robust, US-led response after more than two years of conflict. Photos and video footage of the victims of the attack, many of them young children, led to an international outcry.
With the finger of blame firmly pointing at the Syrian army, the government then sought to avert blame by claiming its soldiers had find chemical weapons in rebel tunnels. US Secretary of State John Kerry called his Syrian counterpart Walid Al Moallem on Thursday to put pressure on the Syrian government  to allow a UN chemical weapons investigative team, already in Damascus looking into previous claims of chemical weapons use, access to the site of Wednesday's attack.
Obama has been reluctant to intervene in the Syrian conflict but previously stated that any use of chemical weapons would be a "red line" for the US. The chemical weapons claims from last week have put pressure on the White House to make good on the president's comments.
As a preliminary measure, the United States is repositioning its naval forces in the Mediterranean to give Obama the option for an armed strike, Reuters reported.
"President Obama has asked the Defense Department to prepare options for all contingencies ," U.S. Defence Secretary Chuck Hagel told reporters in Malaysia as he began a week-long trip to Asia, according to Reuters.
Following Obama's meeting, the White House declined to detail what options were discussed on Saturday and said Washington was still gathering information about the attack.
"In coordination with international partners and mindful of the dozens of contemporaneous witness accounts and record of the symptoms of those killed, the U.S. intelligence community continues to gather facts to ascertain what occurred," it said in a statement, according to Reuters.
American and European security sources have said US and its allied intelligence agencies have made a preliminary assessments that chemical weapons were used by Syrian forces in the attack.
According to Reuters, Obama spoke to Cameron after the White House meeting. A spokesperson for the British prime minister said the two men noted increasing signs of Syrian government culpability.
"They are both gravely concerned by the attack that took place in Damascus on Wednesday and the increasing signs that this was a significant chemical weapons attack carried out by the Syrian regime against its own people," the spokesperson said.
Cameron also spoke to Canadian Prime Minister Stephen Harper. Harper spoke to French President François Hollande.