Speaking at a gathering of the Lowy Institute think tank in Sydney, Carney said Canada welcomed steps to change Iran's form of government -- which he said represented the "principal source of instability and terror" in the Middle East.

But, he said, the action "would appear, prima facie, not to be consistent or to be inconsistent with international law".

"It's a judgement for others to make," he added.

"I'm not a lawyer, let alone an international legal expert."

Carney's comment came on the second day of an official visit to Australia, a trip aimed at bringing in investment and deepening ties with a fellow "middle power" partner.

The trip is part of a multi-country tour of the Asia-Pacific aimed at reducing reliance on the United States -- a hedge against what Carney has described as a fading US-led global order.

The former central banker has frequently clashed with US President Donald Trump, who has frequently threatened to annex Canada and slapped swingeing tariffs on the country.

In a speech to political and financial elites at the World Economic Forum in January, Carney warned the US?led global system of governance was enduring "a rupture".

And on Wednesday the Canadian prime minister said the war in the Middle East represented "another example of the failure of the international order".

"Canada calls for a rapid de-escalation of hostilities and is prepared to assist in achieving this goal," he said.

"Canada reaffirms that international law binds all belligerents," he said.

- US, Israel 'acting without engagement' -

The United States and Israel launched the attack on Saturday and quickly killed Iran's supreme leader, Ayatollah Ali Khamenei, two days after US envoys had been speaking to Iran in Geneva on a nuclear accord.

Since then, Iran has expanded its retaliatory missile and drone barrage across the Middle East, hitting on Tuesday a US consulate and base as the United States and Israel said they had pummeled key sites inside Tehran.

The regional war also took a growing toll on Lebanon, where Hezbollah, the armed Shiite Muslim movement that long had Tehran as a benefactor, launched drones and rockets at Israel in retaliation for Khamenei's slaying.

Carney has backed the Israeli-US strikes targeting Iran, saying Tehran had failed to dismantle its nuclear programme and cease support for militant groups.

But he expressed "regret" on Wednesday that international efforts had failed to disarm Iran.

And he noted that "the United States and Israel have acted without engaging the United Nations or consulting with allies, including Canada".

On Thursday Carney will meet with Prime Minister Anthony Albanese and address parliament in the capital Canberra.

Albanese's office has framed Carney as a like-minded leader and said his trip will focus on economic security and critical minerals -- of which Australia has vast reserves -- as well as defence.