NEW YORK (REUTERS) - Japanese Prime Minister Shinzo Abe, rattled by Donald Trump's campaign rhetoric that cast doubt on longstanding US alliances, meets the American president-elect on Thursday (Nov 17) for talks whose details were arranged only at the last minute.

A day before the afternoon meeting in New York, basic logistics such as the time, the place, and who would be in the room were still up in the air, causing anxiety for Japanese officials who are already nervous about the future strength of a alliance that is core to Tokyo's diplomacy and security.

Trump official Kellyanne Conway said on Thursday morning that Abe would meet Trump and Vice President-elect Mike Pence at Trump Tower in Manhattan at 5pm ET (2200 GMT).

Abe and other Asian leaders were alarmed at Trump's pledge during his election campaign to make allies pay more for help from US forces, his suggestion that Japan should acquire its own nuclear weapons, and his staunch opposition to the Trans-Pacific Partnership (TPP) trade deal.

The meeting will be the Republican Trump's first face-to-face foray into international diplomacy as president-elect.

A brash outsider who has never held public office, Trump has been consumed since winning last week's election with working out who will occupy senior positions in his administration. His transition officials do not yet have access to detailed briefing documents on national security and economic policy.

Conway sought to convey a sense of an informal first encounter with Abe, telling reporters it would not include any "diplomatic agreements" out of deference to President Barack Obama, who does not hand over to Trump until Jan 20.

"Any deeper conversations about policy and the relationship between Japan and the United States will have to wait until after the inauguration," she said in an interview with CBS.

Nevertheless, the last-minute arrangements were unsettling for the Japanese. Abe is a political blue blood and veteran lawmaker who worked closely with Obama, a Democrat, on the 12-nation TPP trade pact, which was part of Obama's push to counter the rising strength of China and a pillar of Abe's economic reforms.

Before leaving Tokyo, Abe said he wanted to build trust with Trump, Kyodo news agency reported. He told reporters that the US-Japan alliance "is the cornerstone of Japan's diplomacy and security. Only when there is trust does an alliance come alive."

Trump fanned worries in Tokyo and beyond with his campaign comments on the possibility of Japan acquiring nuclear arms and demands that allies pay more for the upkeep of US forces on their soil or face their possible withdrawal.

A Trump adviser who spoke on condition of anonymity said earlier this week he expected the president-elect to reaffirm "the American commitment to being in the Pacific long term."

The question of financial support for US troops based in Japan was unlikely to be a focus at the meeting with Abe, the adviser said.

Asked whether the issue would be raised, Conway told CBS: "Maybe they'll discuss that today."

ABE TO STRESS ALLIANCE

Abe adviser Katsuyuki Kawai told Reuters he had spoken to several Trump advisers and lawmakers since arriving in Washington on Monday and had been told, "We don't have to take each word that Mr Trump said publicly literally". "Prime Minister Abe will definitely talk about the importance of the Japan-US alliance and that alliance is not only for Japan and the United States, but also for the entire Indo-Pacific region as well as world politics," he said.

Abe has boosted Japan's overall defence spending since taking office in 2012, while stretching the limits of its pacifist post-war constitution to allow the military to take a bigger global role. Defence spending still stands at just over 1 per cent of GDP compared with more than 3 per cent in the United States.

The United States is projected to spend US$5.745 billion for US forces in Japan in the current 2017 fiscal year. According to Japan's Defence Ministry, Tokyo's expenses related to US troops stationed in Japan totaled about 720 billion yen (S$6.6 billion) in the year that ended in March.

Some of Trump's campaign rhetoric suggested an image of Japan forged in the 1980s, when Tokyo was seen by many in the United States as a threat to jobs and a free-rider on defence.

The Trump adviser who spoke earlier in the week stressed a more positive view.

"Frankly, the Prime Minister has been more assertive and forthright in trying to make those changes to Japan's global posture," he said. "I think he's going to get a very receptive audience there."

Abe was expected to see Obama at a summit in Peru at the weekend. Hours before Abe and Trump were due to meet in New York, Obama's Secretary of State John Kerry and Japanese Foreign Minister Fumio Kishida met in Lima to discuss the Paris climate accord - a deal Trump has pledged to exit.

AT TRUMP TOWER: CABINET POSSIBLES

Some diplomats say that until Trump makes key appointments, it will be hard to assess his policies on security issues ranging from overseas deployments of US troops, China's maritime assertiveness, and the North Korean nuclear threat.

Trump was also meeting on Thursday with people who could fill roles in his administration, including South Carolina Governor Nikki Haley, a potential choice for secretary of state.

He issued a statement praising the "phenomenal record" of Alabama Senator Jeff Sessions, a loyalist touted for the Pentagon and other Cabinet jobs, but said "nothing has been finalised and he is still talking with others."

Trump planned to meet Mitt Romney, Republican presidential candidate in 2012, on the weekend, CNN reported, citing an unidentified source. In a campaign season where many Republican leaders distanced themselves from the unorthodox Trump, Romney was one of the strongest opponents. He urged Republicans while the party was picking its presidential nominee not to back Trump.

Trump also plans to travel to battleground states at the end of the month for a victory "thank you" tour, George Gigicos, his trip director, told reporters.

Pence started his day in Washington, meeting with lawmakers, who said Trump wants to weigh in early on budget and appropriations issues.

Republican congressman Chris Collins, a liaison between lawmakers and the Trump team, said the new administration was poised to move "very quickly" to overturn some of Obama's executive orders, as well as to work on health care and tax reforms.