DAMASCUS -- Momentum appeared to build Tuesday for western military action against Syria, with the U.S. and France saying they are in position for a strike, while the government in Damascus vowed to use all possible measures to repel it.
The prospect of a dramatic U.S.-led intervention into Syria's civil war stemmed from the West's assertion -- still not endorsed by UN inspectors -- that President Bashar Assad's government was responsible for an alleged chemical attack on civilians outside Damascus on Aug. 21 the group Doctors Without Borders says killed 355 people. Assad denies the claim.
The Arab League also threw its weight behind calls for punitive action, blaming the Syrian government for the attack and calling for those responsible to be brought to justice.
British Prime Minister David Cameron recalled Parliament to hold an emergency vote Thursday on his country's response. It is unlikely any international military action would begin before then.
Prime Minister Stephen Harper and U.S. President Barack Obama agreed the use of chemical weapons in Syria requires a "firm response," without defining what such a response might entail.
The two spoke by telephone Tuesday.
Harper's office said the prime minister agreed with Washington's assessment the Syrian regime used chemical weapons against its own people and called it an outrage.
"Both leaders agreed that significant use of chemical weapons merits a firm response from the international community in an effective and timely manner," said Andrew MacDougall, a spokesman for Harper.
The Obama administration said the two men pledged to continue to consult closely on potential responses by the international community.
U.S. Defence Secretary Chuck Hagel said U.S. military forces stand ready to strike Syria at once if Obama gives the order, and French President Franßois Hollande said France was "ready to punish those who took the heinous decision to gas innocents."
Obama is weighing a response focused narrowly on punishing Assad for violating international agreements that ban the use of chemical weapons. Officials said the goal was not to drive Assad from power or impact the broader trajectory of Syria's bloody civil war, now in its third year.
Russian Foreign Minister Sergey Lavrov said Monday the West should be under no illusion bombing Syrian military targets would help end the violence in Syria, an ally of Moscow, and he pointed to the volatile situations in Iraq and Libya he said resulted from foreign military intervention.
Syrian Foreign Minister Walid al-Moallem said his country would use "all means available" to defend itself.
"We have the means to defend ourselves and we will surprise everyone," he said.
At a news conference in Damascus, al-Moallem challenged Washington to present proof to back up its accusations and he also likened the allegations to false American charges in 2003 that Iraq possessed weapons of mass destruction before the U.S.-led invasion of that country.
"They have a history of lies -- Iraq," he said.
The White House dismissed as "fanciful" the notion anyone other than Assad could be to blame.
"Suggestions that there's any doubt about who's responsible for this are as preposterous as a suggestion that the attack did not occur," spokesman Jay Carney said.
A U.S. official said some of the evidence includes signals intelligence -- information gathered from intercepted communications. The U.S. assessment is also based on the number of reported victims, the symptoms of those injured or killed, and witness accounts.
The officials insisted on anonymity because they were not authorized to publicly discuss the internal deliberations.
The United Nations said its team of chemical-weapons experts in Syria had delayed a second trip to investigate the alleged attack by one day for security reasons. On Monday, the team came under sniper fire.
If Obama decides to order an attack against Syria, it would most likely involve sea-launched cruise missile attacks on Syrian military and communications targets.
-- The Associated Press