TOKYO — U.S. Defense Secretary Jim Mattis reassured Japanese leaders today that President Donald Trump is fully committed to defending Japan as a treaty partner.

Trump himself raised doubts about the value of the alliance by saying during his presidential campaign that the security partnership is a bad deal for the U.S.

Mattis was firm in stating that the Trump administration will stand behind Japan. He spoke at the start of a meeting with Prime Minister Shinzo Abe.

Abe welcomed Mattis and said he looked forward to visiting the White House next week.

In South Korea earlier, Mattis delivered an explicit warning to North Korea, asserting that any use of nuclear weapons by the North on the United States or its allies would be met with what he called an “effective and overwhelming” response.