The operation marks the first ship boarding by U.S. forces since the naval blockade took effect April 13, as part of Trump's effort to exert pressure on Tehran.

With only days remaining until a fragile ceasefire expires, U.S. and Iranian negotiations appeared to be no closer to a deal to end the war despite both countries offering optimistic outlooks.

Pakistan helped broker a two-week cease-fire between the U.S. and Iran that expires on Tuesday night.