President Donald Trump has said that the US war on Iran was "small potatoes" for the United States, in his administration's latest bid to play down the conflict ahead of crucial midterm elections.

Trump's comments came a day after Vice President JD Vance said that "I wouldn't call it a war" despite an upsurge in fighting between Iran and the United States over the Strait of Hormuz.

"A lot of people don't call it a war. I call it a military conflict because it's small potatoes for us," Trump told reporters on Friday in the Oval Office when asked about Vance's remarks.

"It's not a big thing. We did Venezuela, and we did this," added Trump, who was surrounded by cattle ranchers invited for the signing of two executive orders on beef processing.

US joined Israel in attacking Iran on February 28, with strikes quickly killing the longtime supreme leader, Ali Khamenei, and much of the other top brass as well as hundreds of civilians.

But Iran quickly hit back by exerting control over the Strait of Hormuz, the narrow passageway through which one-fifth of global oil once sailed, and it has rained missiles and drones on US-allied Gulf Arab monarchies, shattering the oil-rich countries' hard-earned reputation for stability.

We took over Venezuela — Trump

The six-month-old war in which 18 US troops and thousands of Iranians have been killed, including women and children, has reached a stalemate, with Tehran disrupting shipping traffic in the strategic waterway.

But with fuel prices threatening to cost Trump's Republicans their control of Congress in November's midterms, his administration appears to be trying to minimise the conflict.

Trump said the US was carrying out "intermittent strikes" but that "we're not fighting right now."

He reiterated his claims that the United States effectively controlled the Strait of Hormuz and had decimated Iran's military.

"What we've done is amazing. We took over Venezuela and we have essentially taken over Iran," Trump said.

Pressed on calling the war "small potatoes" when 18 service members have been killed, an increasingly irate Trump compared the Iran war to the years-long US wars in Vietnam and Afghanistan.

"I don't think it matters what you call it. What matters is the fact we have had tremendous success. We've stopped Iran from having a nuclear weapon," he said.