Canberra, Australia - Canadian Prime Minister Mark Carney said on Thursday that he couldn't rule out military participation in the escalating conflict triggered by President Donald Trump's war with Iran.

Speaking in a joint press conference with Australian Prime Minister Anthony Albanese in Canberra, Carney was asked whether there was a situation in which Canada would get involved in the escalating conflict in the Middle East.

"One can never categorically rule out participation," he said. "We will stand by our allies when it makes sense... We will always defend Canadians; we will always stand by and defend our allies when called upon."

Carney stressed that there is a difference between participating in the offensive war undertaken by the US and Israel and participating in defensive actions supporting allies and Canadians. He also pointed out that the US had not consulted its allies before embarking on the war on Iran.

Carney's comments came a day after he suggested the US-Israeli strikes could Iran might be "inconsistent with international law" and called for a "rapid de-escalation of hostilities."

Carney's visit to Australia this week has in many ways been overshadowed by an expanding war in the Middle East, sparked by President Donald Trump's decision on Saturday to launch a massive attack on Iran.

The operation, which was conducted jointly with the Israelis, saw Ayatollah Ali Khamenei killed in an airstrike and sparked a wave of retaliatory strikes across the Middle East.

While Carney has condemned Trump's attack on Iran, he has expressed support for efforts to stop Tehran from obtaining a nuclear weapon.

"There are no certainties in conflict," Carney said when asked about why he didn't immediately call for de-escalation. "Now that the conflict has moved on... It is not solely the decision of the belligerents to move to de-escalation."

On Thursday morning, Carney issued a rallying cry in Australia's parliament to "middle powers," including Canada and Australia, urging them to work together in an increasingly hegemonic world order.

His remarks reaffirmed views he has expressed since he announced an end to the old world order during his speech to the World Economic Forum in January.

Nations like Australia and Canada faced a stark choice, Carney told Australia's parliament on Thursday, and must either work together to help write the "new rules" of the global order or have great powers do it for them.

"In this brave new world, middle powers cannot simply build higher walls and retreat behind them. We must work together," he said.

"Great powers can compel, but compulsion comes with costs, both reputational and financial," the former central banker added.

"Middle powers like Australia and Canada hold this rare convening power because others know we mean what we say and we will match our values with our actions."