A spokesman for Foreign Affairs Minister John Baird said the continuing violence in Syria — which critics say has claimed 14,000 lives — is "rapidly spiralling out of control."
"It is crucial we reach a diplomatic solution to the crisis before the situation deteriorates any further," Rick Roth said.
Canada's call for action followed a meeting in Geneva which accepted a UN-brokered peace plan calling for the creation of a transitional government in Syria.
But, at Russia's insistence, the compromise agreement left open the possibility of embattled Syrian president Bashar Assad being part of the new government.
Baird's spokesman said Canada supports the UN plan and believes it "remains the best hope" for a quick, peaceful resolution to the conflict.
But Canada feels Assad cannot continue to lead the country, he said.
"Assad can not remain President as those working for peace in Syria will likely find his presence to be a deal-breaker," Roth said.
He added, however, that Canada knows it must be realistic and will continue to pursue any avenue that will bring a lasting peace.
Canada is also calling for Syria's religious and cultural minorities to be respected and protected and for the country's women to play a central role in any rebuilding efforts.
"The Syrian people must collectively decide for themselves a path towards the better, brighter future they all crave," Roth said.
It's unclear if the UN plan will have any real effect to curbing the violence in Syria.
A key phrase in the agreement requires that the transitional governing body "shall be formed on the basis of mutual consent," effectively giving the present government and the opposition veto power over each other.
Syrian opposition figures immediately rejected any notion of sharing in a transition with Assad, though the agreement also requires security force chiefs and services to have the confidence of the people.
Assad's government had no immediate reaction, but he has repeatedly said his government has a responsibility to eliminate terrorists and will not accept any non-Syrian model of governance.
More than a year into the uprising, Syria's opposition is still struggling to overcome infighting and inexperience, preventing the movement from gaining the traction it needs to instill confidence in its ability to govern.
The United Nations says violence in the country has worsened since a cease-fire deal in April, and the bloodshed appears to be taking on dangerous sectarian overtones, with growing numbers of Syrians targeted on account of their religion.
The increasing militarization of both sides in the conflict appears to have Syria headed toward civil war.
— with files from the Associated Press