US President Donald Trump has greeted Japan's Prime Minister Sanae Takaichi warmly at the White House and says he believes Japan is "really stepping up to the plate" on Iran unlike the NATO military alliance.
Trump has criticised allies for their lukewarm support for the US-Israeli military campaign and said the United States does not need any help.
However, he is still pushing for more ships to clear mines and escort tankers through the Strait of Hormuz, largely closed by Iran in the conflict.
Ahead of the meeting, Japan joined several European countries in a joint statement, saying they would take steps to stabilise energy markets and were ready to join "appropriate efforts" to ensure safe passage through the Strait.
Trump hailed Takaichi's election victory last month as "record setting" as he welcomed her at the Oval Office.
He said they would "be talking about trade and many other things" including Iran.
"We've had tremendous support and relationship with Japan on everything, and I believe that based on statements that were given to us yesterday, the day before yesterday, having to do with Japan, they are really stepping up to the plate ... unlike NATO," Trump said.
He said he expected Japan to step up given the support the US gave the country and the tens of thousands of troops it has stationed there.
"We don't need much; we don't need anything," Trump said.
"We don't need anything from Japan or from anyone else. But I think it's appropriate that people step up."
Takaichi told Trump she had "brought specific proposals to calm down the global energy market" and said Iran must never be allowed to obtain a nuclear weapon.
She condemned Iran's attacks in the Strait of Hormuz and said she believed only Trump could achieve peace.
She also said the global economy was about to take a hit due to the turmoil in the Middle East.
Takaichi's long-scheduled White House visit has been aimed at burnishing the decades-old security and economic partnership between the two countries.
Takaichi has sought to move Japan away from a pacifist constitution imposed by the US after World War II but with the Iran war unpopular at home, she has so far not offered to assist in clearing the Strait of Hormuz.
US Treasury Secretary Scott Bessent earlier said he would expect that Japan, which gets 95 per cent of its crude oil supplies from the Gulf, would want to ensure its supplies are safe.
Bessent told Fox Business Network that Japan's navy has some of the best minesweepers and mine-detection capabilities.
He said he believed Japan would release more of its large petroleum reserve to supply the strained oil market.
Takaichi told the Japanese parliament on Monday that Japan had received no official request from the United States on Iran but was checking the scope of possible action within the limits of its constitution.
Shortly before heading to Washington, Takaichi posted on X that she would discuss "the increasingly tense situation surrounding Iran".
She also said she would "confirm with President Trump the unwavering bond between Japan and the United States and further promote co-operation across a wide range of areas, such as security and the economy".