A visit by a U.S. aircraft carrier to South Korea prompted a warning from the sister of North Korea’s leader that Washington and Seoul “should not test” the communist regime.

USS Carl Vinson (CVN-70) pulled in to Busan Naval Base, South Korea on Sunday for a scheduled port visit, marking the first visit of a U.S. carrier to a foreign port during the second Trump administration.

The Carl Vinson Carrier Strike Group arrived in South Korea only days after Pyongyang carried out its fourth missile test this year.