Two U.S. supersonic B-1 Lancer strategic bombers flew over South Korea on Tuesday.

A U.S. military official says the move demonstrates the country’s solidarity with its ally. Seoul says Pyongyang is preparing the detonation of another nuclear device.

The U.S. special envoy on the DPRK has met with his South Korean counterpart Kim Hong-kyun in Seoul. The two held a press conference after the meeting.