Sherman will visit Tokyo from Monday through Wednesday, meeting senior officials and also holding joint three-way talks with the vice foreign ministers of Japan and South Korea, both US allies.

"Together with the international community, we call on the DPRK to refrain from further provocations and engage in sustained and substantive dialogue," said a senior US official who is scheduled to travel with Sherman, using the North's official name, the Democratic People's Republic of Korea.

President Joe Biden has offered working-level talks but has found little interest from North Korea, whose leader Kim Jong Un met three times with Biden's predecessor Donald Trump, reducing tensions but resulting in no lasting agreement.

North Korea's launches have included firing a missile over Japan. The United States has moved to tighten sanctions in response, although efforts at the United Nations have been blocked by Pyongyang's main ally China.

The US official due to make the trip with Sherman said the United States remained ready to talk to North Korea "without any preconditions whatsoever."

"Our goal remains the complete denuclearization of the Korean Peninsula. We remain prepared to engage in serious and sustained diplomacy to make tangible progress towards that end," the official told reporters on customary condition of anonymity.

"It is unfortunate that the DPRK has not responded to our outreach, but we will continue."

In Japan, Sherman will also hold a roundtable with LGBTQ community leaders and discuss marriage equality, the official said.

President Joe Biden's administration has promised to prioritize LGBTQ rights on the global stage and Japan is seen a country where US encouragement could make an impact.

Japanese local authorities, notably in Tokyo, have moved to begin recognizing same-sex partnerships, although a court in Osaka in June rejected arguments that the country's ban on same-sex marriage is unconstitutional.