WASHINGTON (AP) — A senior U.S. envoy will hold joint talks about North Korea next week with Japan and South Korea, and then with China.

The latest round of regional diplomacy on how to deal with the unpredictable government of Kim Jong Un (kim jawng oon) comes as North Korea steps up claims of its nuclear and missile capabilities.

Earlier this month, North Korea said it had test-launched a new type of missile from a submarine. This week, the powerful National Defense Commission said the North could miniaturize a nuclear weapon.

The State Department says U.S. special representative for North Korea policy Sung Kim will hold talks in Seoul starting Tuesday with his South Korean and Japanese counterparts.

He then goes to Beijing on Thursday to meet with his Chinese counterpart.