The commander of US forces in South Korea, General Robert Abrams, and the head of that country's joint chiefs of staff, General Park Han-ki, "are looking at scaling back the command post training due to concerns about the coronavirus," US Defense Secretary Mark Esper said at a news conference.

His South Korean counterpart, Jeong Kyeong-doo, said at the same briefing that 13 servicemen from his country have become infected with the virus and that all leave for the military has been cancelled nationwide so as to limit soldiers' movements.

"The situation is quite serious," Jeong said.

The two countries have significantly scaled back traditional joint military exercises so as to facilitate US nuclear talks with North Korea.

This spring they planned to hold a command coordination exercise.