The two spoke by telephone Tuesday even as the possibility of a U.S.-led strike against the rogue regime of Bashar Assad loomed larger and the U.S. defence secretary said American military forces were ready to attack if ordered.
Harper's office said the prime minister agreed with Washington's assessment that 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.
The possibility of military strikes comes even though UN inspectors on the ground in Syria have yet to confirm the use of chemical agents.
Harper and Obama discussed the inspection effort.
"Both leaders noted efforts by the Syrian regime to delay the work of the UN chemical inspection team, suggesting the regime is attempting to obscure evidence of its actions," MacDougall said.
In Britain, Prime Minister David Cameron recalled Parliament for an emergency vote on Thursday in response to the alleged chemical assault.
The Arab League flatly blamed the Syrian government for the attack that activists say killed hundreds of people last week. The league said the perpetrators must be brought to justice.
Syrian Foreign Minister Walid al-Moallem denied his government was behind the attack and challenged Washington to present proof of its accusations.
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