U.S. officials launched an effort to reopen the strait. Military officials say they sank six Iranian small boats trying to target commercial vessels.

U.S. Admiral Brad Cooper, the head of Central Command, declined to comment on whether he thought a ceasefire begun on April 8 remained in effect.

U.S. forces have shot down multiple Iranian missiles and drones and destroyed six small boats, a top U.S. admiral said Monday. The hostilities occurred...