An Australian premier has called US Vice President JD Vance a “knob” before quickly admitting it was unprofessional.

WA Premier Roger Cook was taking part in a “finish the sentence” game with a journalist at a leadership forum in Perth on Tuesday.

The reporter prompted the Labor leader by starting the sentence, “JD Vance is a …”

Cook quickly blurted out “knob”, which drew laughter and then light applause from the gathering.

“Sorry, you’ve got to have one unprofessional moment on stage,” he said.

Federal Treasurer Jim Chalmers was later questioned about Cook’s comment and said he personally wouldn’t have used the same description.

“It’s up to Roger Cook to choose his own words,” Chalmers said.

“I would choose different words. I’m not making any judgments about the words that Roger chose.”

Chalmers was asked if calling the US vice president a “knob” would hurt Australia’s efforts to avoid threatened tariffs on steel and aluminium.

“You know I’ve been asked on a number of occasions now to comment on announcements and things being said by the American administration,” Chalmers said.

“I point out today, as I’ve pointed out on every other occasion, the Americans speak for the American administration, we speak for the Australian government. That’s our job.”

In other happenings on Tuesday (AEDT), US President Donald Trump paused military aid to Ukraine following his clash with President Volodymyr Zelensky last week, deepening the fissure that has opened between the one-time allies.

Trump also said 25 per cent tariffs on goods from Mexico and Canada would take effect within hours, stoking fears of a trade war in North America and sending financial markets reeling.

Vance has come under worldwide criticism for his behaviour berating Ukraine President Volodymyr Zelensky during a media briefing at the White House on Saturday (AEDT).

Vance led the attack on Zelensky, accusing him of being ungrateful to the US and claiming that the Ukraine president was involved in “propaganda”.

He went so far as to criticise Zelensky for not wearing a suit to the Oval Office, despite billionaire Elon Musk donning jeans and t-shirts in the formal setting.

Protesters lined the streets in Warren, Vermont. Photo: X

The day after President Trump and Vance’s extraordinary ganging up on Zelensky, Vance was hounded by protesters accusing him of being “Putin’s puppet” when he took his family skiing in Vermont.

Hundreds of people lined the streets and slopes of Sugarbush Resort, in Warren, waving placards calling Vance a “Nazi” and “traitor” and telling him to “Go ski in Russia”.

Media reported that Vance and his family were whisked away to an undisclosed location.

Trump has lurched toward Russia since taking over as president, shocking traditional allies in Europe and beyond and leaving Ukraine increasingly vulnerable.

The already-tense meeting blew up when Vance stressed the need for diplomacy to resolve the biggest conflict in Europe since World War Two.

Zelensky, his arms folded, countered that Putin could not be trusted and noted that Vance had never visited Ukraine.

“What kind of diplomacy are you talking about, JD?” Zelensky asked after recounting failed diplomatic efforts with Russia.

“I’m talking about the kind of diplomacy that’s going to end the destruction of your country,” Vance shot back.

Zelensky openly challenged Trump over his softer approach toward Putin, urging him to “make no compromises with a killer”.

Zelensky, asked during an interview by Fox News if his relationship with Trump could be salvaged after Friday’s eruption, said, “Yes of course” and appeared to express some regret, adding “I’m sorry for this”.

-with AAP