The U.S. deputy secretary of state says the U.S. plans to cooperate with South Korea, Japan, China and Russia for the complete and verifiable denuclearization of North Korea.

James Steinberg made the remarks while visiting Japan to discuss the North Korean nuclear problem.

He said that during his meeting with Japanese officials, Washington and Tokyo reaffirmed both their cooperative status and the U.S. promise to ensure Japan’s security.

Steinberg added that the U.N. Security Council and other concerned parties have had productive discussions on how best to respond to the recent series of controversial acts by North Korea, including nuclear and missile tests.