Abe is set to join Obama in Hawaii on December 26 and 27, several weeks after the 75th anniversary of the surprise bombing on December 7, 1941. By doing so, the prime minister would become the first Japanese leader to visit Pearl Harbor.

The symbolic move has sparked speculation that Abe might officially apologize for the attack that killed 2,400 US servicemen and dragged the US into World War II. Abe's cabinet secretary, Yoshihide Suga, denied the rumors on Tuesday.

"This visit is for the sake of consoling the souls of those who died in the war, not for the sake of an apology," Suga said in Tokyo.

Also, the two-day summit would present an opportunity "to demonstrate to future generations our resolve not to repeat the horror and suffering of war as well as an opportunity to showcase the reconciliation between Japan and the United States," the spokesman added.

US-Japan alliance threatened under Trump?

Observers believe that the diplomatic visit is also aimed at Japan's rival China, underscoring the close ties between Tokyo and Washington before Obama leaves office. His successor, Donald Trump, has criticized Tokyo during the campaign for not paying the US enough for defense. He also said that Washington must always be "prepared to walk" away from the decades-old alliance.

Abe met with Trump in New York last month.

Earlier this year, Obama  became the first sitting president to visit Hiroshima and pay his respects to victims killed after the US dropped an atomic bomb on the city in 1945. However, he did not apologize for using nuclear arms.

The US occupied Japan after its defeat in 1945, but the two countries have since forged very close ties and present a united front against the potential threats of China and North Korea. Japan still hosts a number of US military bases with some 54,000 troops and pays $1.7 billion (1.58 billion euros) a year for their support.

dj/kms (AFP, AP, Reuters)