DUBAI, United Arab Emirates — Iran’s supreme leader said Thursday that the Islamic Republic will protect its “nuclear and missile capabilities” as a national asset, likely seeking to draw a hard line as U.S. President Donald Trump presses for a wider deal to cement the war’s shaky three-week ceasefire.

Ayatollah Mojtaba Khamenei maintained the defiant tone he has struck since taking over as supreme leader following the killing of his father in the war’s opening airstrikes. In a written statement read by a state television anchor, Khamenei — who has not been seen in public since becoming supreme leader — said the only place Americans belonged in the Persian Gulf is “at the bottom of its waters” and that a “new chapter” was being written in the region’s history.

His remarks come as Iran’s oil industry is being squeezed by a U.S. Navy blockade halting its oil tankers from getting out to sea.…