During Donald Trump's administration, America's Asian allies often questioned whether Washington would uphold long-standing promises to defend them in the event of a military attack.

Trump had publicly mulled withdrawing troops from Japan and South Korea, where more than 20,000 US military personnel are stationed to deter any North Korean military action.

Biden and Suga both urged denuclearization of the whole Korean peninsula in the call -- their first since Biden took office last week.

They discussed Washington's "unwavering commitment to the defense of Japan under Article 5 of our security treaty," the White House said in a statement, and Biden reaffirmed "his commitment to provide extended deterrence to Japan."

The US backing "includes the Senkaku Islands" -- an area claimed both by Japan and China, which calls the islands the Diaoyus, the statement said.

They also "discussed regional security issues, including China and North Korea. They together affirmed the necessity of complete denuclearization of the Korean Peninsula."

Suga agreed to visit the United States as soon as possible, but the two leaders did not discuss the postponed Tokyo Olympic Games, which could again be threatened by the pandemic, the Jiji Press agency said.

US Secretary of State Antony Blinken also spoke Wednesday with Japanese Foreign Minister Toshimitsu Motegi and stressed Biden's pledge to "engage with the world again," a State Department spokesman said.