Trump, on his longest journey abroad since taking office in January, announced deals with four Southeast Asian countries during the first stop in Malaysia and will conclude his trip at a summit with Chinese President Xi Jinping on Thursday.
Negotiators from the world's top two economies hashed out a framework on Sunday for a deal to pause steeper American tariffs and Chinese rare earths export controls, US officials said - news that drove Asian stocks to record peaks.
Trump's Treasury Secretary Scott Bessent, who was among the travelling delegation, said the overall framework of a deal with South Korea was also done but would not be finalised this week.
Trump has already landed a $US550 billion ($A842 billion) investment pledge from Tokyo in exchange for respite from punishing import tariffs.
Japan's newly elected Prime Minister Sanae Takaichi is hoping to further impress Trump with promises to purchase US trucks, soybeans and gas at a summit meeting on Tuesday.
Takaichi, who became Japan's first female premier last week, told Trump strengthening their countries' alliance was her "top priority" in their first phone call on Saturday.
Trump said he was looking forward to meeting Takaichi, a close ally of his late friend and golfing partner, former Prime Minister Shinzo Abe, adding, "I think she's going to be great".
Thousands of police have been deployed across the Japanese capital for Trump's arrival, with the arrest of a knife-wielding man outside the US embassy on Friday and an anti-Trump protest planned in downtown Shinjuku adding to the tension.
Commerce Secretary Howard Lutnick and his Japanese counterpart Ryosei Akazawa, architects of the tariff deal agreed in July, are set to hold a working lunch on Monday.
Bessent, travelling with Trump alongside Secretary of State Marco Rubio, is also expected to meet his new counterpart, Satsuki Katayama, for the first time.
Trump was the first foreign leader to meet Naruhito after he came to the throne in 2019, continuing an imperial line that some claim is the world's oldest hereditary monarchy.
Naruhito's role, however, is purely symbolic and it will be with Takaichi on Tuesday that the meaty diplomacy will take place.
The two are due to meet at the nearby Akasaka Palace, the venue where Trump met Abe six years ago, and will be welcomed by a military honour guard.
Takaichi is expected to reassure Trump that Tokyo is willing to do more on security after telling MPs on Friday she would accelerate Japan's biggest defence build-up since World War II.
Japan hosts the biggest concentration of US forces abroad and Trump has previously complained that Tokyo is not spending enough on defending its islands from an increasingly assertive China.
"Some kind of statement on standing shoulder-to-shoulder together to deter and respond to attempts to change the status quo in the region by force or coercion would be useful," said Kevin Maher, a Japan expert at NMV Consulting in Washington and former US diplomat.
While Takaichi has said she will accelerate a plan to increase defence spending to two per cent of GDP, she might struggle to commit Japan to any further increases that Trump asks for, as her ruling coalition does not have a majority in parliament.
Trump is due to leave on Wednesday for Gyeongju, where he will first hold talks with South Korean President Lee Jae Myung.
