Harper blamed last month's attack on civilians on the regime of Syrian President Bashar al-Assad, as he spoke at the close of the G20 Summit in St. Petersburg, Russia.
Canada is one of the signatories of a joint statement on Syria issued by the White House Friday that condemns the alleged attack that "that claimed the lives of so many men, women, and children" and places the blame squarely on the Assad regime.
"The evidence clearly points to the Syrian government being responsible for the attack, which is part of a pattern of chemical weapons use by the regime," the statement said.
"We call for a strong international response to this grave violation of the world’s rules and conscience that will send a clear message that this kind of atrocity can never be repeated. Those who perpetrated these crimes must be held accountable," said the statement, which also expresse support for the United States' recent efforts to "reinforce the prohibition on the use of chemical weapons."
Other signatories include Australia, France, Italy, Japan, Republic of Korea, Saudi Arabia, Spain, Turkey and the United Kingdom.
Describing the discussion among leaders at the summit, Harper called the talk about Syria "extremely frank, but I think also respectful ... of what are very large divergences of opinion around the table."
"We share the view of our allies that the use of chemical weapons on an unprecedented scale by the Syrian regime constitutes a very troubling development," Harper said Friday.
"And if it is not countered, it will constitute a precedent that we think is very dangerous for humanity in the long term. And so, obviously, we are very supportive of those of our allies who want to take action to try and prevent this development from going further, trying to dissuade the Syrian regime from this course of action."
Harper also announced an additional $42 million in funding for humanitarian organizations to provide food, water, shelter and other help to refugees from the region.
The civil war Syria has driven an estimated two million people into neighbouring Lebanon, Jordan and Turkey. The extra $42 million brings the total committed by Canada since January 2012 to $203.5 million.
The G20 Summit, which wrapped up Friday, provides a regular opportunity for the leaders of the 20 biggest economies in the world to discuss economics, but the Syrian crisis drove many governments to send their foreign affairs ministers along to discuss possible solutions.
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