U.S. Ambassador to South Korea Sung Kim said if North Korea wants to improve relations with the U.S., it should first work with South Korea.

Kim was speaking on U.S. policy on Northeast Asia and the Korea-U.S. alliance at a forum on Wednesday.

“We have continued to make it clear to Pyongyang both publicly and privately that they cannot bypass Seoul,” Kim said.

“If they want to deal with important issues, concerns, if they want to improve relations with the U.S., if they want come back to negotiations in the six-party process, they have to work with South Korea.”

The conference, the Foreign and Trade Policy Symposium, was organized by the Asia-Pacific Policy Research Institute, a private think tank.

Kim, the first Korean-born U.S. ambassador to Korea, formerly served as Washington’s special envoy for the six-party talks, which have been aimed at North Korea’s denuclearization since 2008.

He made it clear that the recent rocket launch by the North was a missile launch and that it violated “all sorts of existing commitments” including U.N. Security Council resolutions.

However, the U.S. still hopes that Pyongyang will focus on more constructive efforts such as “helping its people” rather than developing “dangerous weapons,” he said.

Kim stressed that the challenge of North Korea is an important part of U.S. cooperation with China.

“As President Obama said, what we want with China is to have a cooperative relationship based on mutual interest and mutual respect,” he said.

Senior U.S. officials including Secretary of State Hillary Clinton and Secretary of the Treasury Timothy Geithner will visit Beijing soon for strategic and economic dialogue with China, he said.

By Kim Yoon-mi (yoonmi@heraldcorp.com)