A top U.S. envoy has visited Vietnam to hold talks on expanding cooperation to prevent the spread of weapons of mass destruction.

The State Department said Assistant Secretary of State Thomas Countryman spoke with officials in Hanoi on Wednesday and Thursday.

In a statement, Countryman said Vietnam has demonstrated a serious commitment to cooperating with the U.S. on non-proliferation.

He referred to Vietnam's promise to convert a nuclear research reactor from producing highly enriched uranium to low-enriched uranium, and to its commitment to participate in the Global Initiative to Combat Nuclear Terrorism.

Countryman said the U.S. hopes Vietnam will continue to show leadership on non-proliferation in regional and global affairs.

Countryman is on a visit to the region that includes stops in Indonesia, Malaysia and Thailand.

The State Department says his goal is to hold talks on non-proliferation cooperation, including issues related to the upcoming East Asia Summit. Indonesia hosts the summit in November.