BEIJING — U.S. Defense Secretary Jim Mattis and his Chinese counterpart are striking a positive note as they sat down to tackle the thorny issue of how to get North Korea to fulfill a pledge to abandon its nuclear program.

Mattis says he and Defense Minister Wei Fenghe opened discussions in Beijing on Wednesday with a “very open and honest dialogue.” Wei says the visit is important to increase strategic trust and enhance the cooperation between them.

Neither mentioned specific issues but North Korean denuclearization is expected to top the agenda.

The visit also comes amid sharp U.S. criticism over China’s militarization of its island holdings in the South China Sea and a brewing trade war between the world’s two largest economies.