OTTAWA -- Prime Minister Justin Trudeau says new information received Thursday night from Canada's trusted ally the United States persuaded him that Syrian President Bashar Assad was responsible for the chemical weapons attack on his people this week.
The government was briefed about an hour before a barrage of U.S. cruise missiles was launched Thursday against an airbase in Syria, said Trudeau. He then spoke by phone Friday with President Donald Trump.
The strike prompted an abrupt change in Trudeau's position: after stopping short Thursday of directly blaming Assad, he accused the Syrian government on Friday of using chemical weapons against its own people.
The Conservative opposition seized on Trudeau's comments and accused him of flip-flopping.
But Trudeau made clear he received new information from a credible source, telling reporters in Nova Scotia: "A trusted and reliable ally in the United States informed us that the Assad regime was responsible for these chemical attacks."
Trump and Trudeau discussed the need for a "political solution" to the Syria crisis, the Prime Minister's Office said in a brief synopsis of the call.
Trudeau disclosed the discussions during a long-awaited statement Friday in the House of Commons following Thursday's strike, Trump's response to a gruesome chemical attack Monday in Syria that killed more than 80 civilians.
Trudeau said that about an hour before the U.S. attack, U.S. Defence Secretary Jim Mattis called Defence Minister Harjit Sajjan, who then briefed the prime minister.
"This morning I spoke with the president directly and emphasized that Canada agrees that Assad's repeated use of chemical weapons must not continue," Trudeau said during question period.
"In the face of such heinous war crimes, all civilized peoples must speak with one voice."
The PMO's readout of the call said the two leaders agreed "that the repugnant chemical attacks cannot be permitted to continue with impunity. They also committed to continuing to seek a political solution to end the crisis in Syria.
Conservative MP Pierre Poilievre asked Trudeau to explain the pivot, but the prime minister would only reiterate his support of the U.S. action.
Trudeau said Canada supports the "limited focused action" by the U.S. He also denounced the use of chemical weapons, saying "the crimes the Syrian regime has committed against its own people cannot be ignored."
On Thursday in New York, the prime minister promised that Canada would be involved in the United Nations process to investigate and punish the perpetrators of the chemical attack which left ghastly images of suffering that shocked the world.
Earlier this week, Foreign Affairs Minister Chrystia Freeland said the facts behind the attack had to be clearly established so that those responsible could be held accountable. She said the findings needed to be presented in a "highly credible international fora" so they could not be disputed. She also stopped short of blaming Assad.
Canada and the U.S. are the two leading financial backers for the UN organization that investigates the use of chemical weapons.
Poilievre urged Trudeau not to wait for the UN Security Council -- a body where Russia, which supports Assad's government, wields a veto -- to take action.
"When will the prime minister stop being so dangerously naive and confront this dictator and this tyrant?"
Asked whether former Conservative prime minister Stephen Harper should have pushed former U.S. president Barack Obama to intervene in the war years ago, Poilievre said the circumstances have changed.
"There's a different administration in Washington and, as a result, there's different consequences for the crimes against humanity that the Assad regime is committing," Poilievre said outside the House. "It's too late for the countless civilians who have died already, but it's better late than never."
The New Democrats, meanwhile, wanted to know whether the missile strike is part of a larger strategy and called for a multilateral response.
"We don't know what the long-term plan is. We don't know the kind of information the prime minister may or may not have," said NDP House leader Murray Rankin. "This is a very volatile region. The impact of what he is doing remains of course uncertain."
Russia is the main backer of Syria and has used its Security Council veto to block all UN attempts to take action in the war-torn country.
The Kremlin also sent its military to Syria in 2015 to prop up Assad's government against rebel forces.