Japanese Prime Minister Ishiba Shigeru has congratulated Donald Trump over the phone on his victory in the US presidential election.

Ishiba and Trump spoke for about five minutes on Thursday morning, Japan time.

Ishiba extended his congratulations to Trump, saying he respects that the former president's appeal to "make America great again" won support from many Americans.

Trump responded that he looks forward to talking with Ishiba in person, and the two confirmed they will try to schedule a meeting as soon as possible.

They also agreed to raise the Japan-US alliance to a higher level.

Ishiba later spoke to reporters about the conversation. He said he got the impression that Trump is friendly and that he could speak with him frankly, without using fancy words.

Ishiba was asked how he would respond if Trump asks Japan to shoulder a greater cost to keep US forces in the country. He responded that the issue is complicated and involves various financial and operational problems.

He added he would engage in discussions from various perspectives to bolster the alliance.