Donald Trump says he is “very surprised” Australia has not sent warships to aid in opening the strait of Hormuz as the blockade of the key strategic route for global oil supply continues to impact fuel prices.

“I was very surprised,” the US president said in Washington on Friday when asked what he took issue with regarding Japan, South Korea and Australia.

“Well, they should get involved and I was a little bit surprised that they said no, because we always say yes to them,” he told Sky News Australia.

Trump did not answer when asked what Australia had said no to.

Earlier this week, Trump slammed Japan, Australia and South Korea for saying they would not be sending warships to the Gulf.

“The United States has been informed by most of our NATO ‘Allies’ that they don’t want to get involved with our Military Operation against the Terrorist Regime of Iran, in the Middle East,” the social media post read.

“We no longer ‘need’ or desire, the NATO Countries’ assistance – WE NEVER DID! Likewise, Japan, Australia, or South Korea.”

Also on Friday, the president lashed out at Nato, describing alliance members as “cowards” for not wanting “to help open” the strait of Hormuz.

The globally important shipping lanes between Oman and Iran have been closed since shortly after the latest Middle Eastern conflict began three weeks ago, sending shockwaves through fuel markets.

The International Energy Agency has warned the conflict, prompted by US-Israel strikes on Iran in February, is the “greatest threat to global energy supply in the history of the world”.