Japan is one of the closest allies of the United States in Asia with around 54,000 US military personnel stationed in the country.

Ishiba will be pushing for reassurance on the importance of the US-Japan alliance, as Trump's "America First" agenda risks encroaching on the nations' trade and defence ties.

He may also propose increasing imports of US natural gas, local media said, chiming with Trump's plan to "drill, baby, drill" while boosting energy security for resource-poor Japan.

"The intention is to present a win-win value proposition from Ishiba to the president," Sheila Smith, senior fellow at the Council on Foreign Relations, told AFP.

Also, "Japan has cut its liquefied natural gas (LNG) imports from Russia. So Japan desperately needs to open up new sources of LNG, and other energy more broadly," she said.

Trump will meet Ishiba in Washington on Friday -- just days after a joint press conference with Israeli Prime Minister Benjamin Netanyahu, where the US president sparked uproar with a proposal to take over the Gaza Strip.

The Japan summit could be less startling, Smith said, as Trump "has a fairly strong commitment to the alliances in Asia".

"This is probably a very calm, cool reassurance meeting," she said.

- Taiwan threat -

Ishiba has stressed the importance of US defence ties, pointing to threats on Japan's doorstep such as China pressing its claims of sovereignty on the self-ruled island of Taiwan.

Tokyo must "continue to secure the US commitment to the region, to avoid a power vacuum leading to regional instability", Ishiba told parliament last week.

Trump and Ishiba are expected to affirm the importance of peace and stability in the Taiwan Strait, Japanese media reports said.

That would echo joint statements made by the last US president Joe Biden with previous Japanese prime ministers.

Focusing on this point is "extremely important" because Japan and the United States must work together to prevent a potential crisis, said Takashi Shiraishi, a professor and international relations expert at the Prefectural University of Kumamoto.

Both sides also plan to state Washington's "unwavering commitment" to Japan's defence, the Yomiuri daily reported.

As Japan and the United States renegotiate how to share the burden of defence costs, however, there are concerns Trump could provide less cash and push Japan to do more, Smith said.

"That's where... the Ishiba-Trump relationship could get a bit sticky," she said.

- After Abe -

Trump's willingness to slap trade tariffs on major trading partners Canada, Mexico and China has also caused jitters.

"I hope Ishiba will show him there are other ways to achieve economic security," such as cooperating on technology, Shiraishi told AFP.

One example is the Stargate drive, announced after Trump's January inauguration, to invest up to $500 billion in AI infrastructure in the United States, led by Japanese tech investment behemoth SoftBank Group and US firm OpenAI.

Reports said the leaders could also discuss Nippon Steel's $14.9 billion bid to buy US Steel, which Biden blocked on national security grounds.

Japan and the United States are each other's top foreign investors, a point Ishiba could stress during the talks.

During his first term Trump and Japan's then-prime minister Shinzo Abe, enjoyed warm relations.

As president-elect in December, Trump also hosted Akie Abe, the widow of Japan's assassinated ex-premier for a dinner with Melania Trump at their Florida residence.

Trump built a strong relationship with Abe, for whom Smith believes he had a "genuine fondness".

He will likely "see Ishiba through a different lens," said Smith from the Council on Foreign, and "it will be more the state-to-state relationship, not the personal".

Ishiba, 68, will not be the first Japanese VIP to meet the 78-year-old President Trump in person since he took office -- an accolade held by SoftBank founder Masayoshi Son.