President Trump warned Friday night that he may not extend the U.S.-Iran ceasefire when it expires Tuesday, April 21, and threatened to resume bombing Iran if no deal is reached.

Speaking to reporters aboard Air Force One, Trump said: “I don’t know. Maybe I won’t extend it, but the blockade is going to remain. But maybe I won’t extend it, so you’ll have a blockade and unfortunately we’ll have to start dropping bombs again.”

The comments came hours before Iran announced Saturday it had reimposed control of the Strait of Hormuz in response to the continued U.S. blockade of Iranian ports. Iran called the blockade a ceasefire violation.

Pakistani Foreign Minister Ishaq Dar said Pakistan is working to “bridge” differences between the U.S. and Iran. A second round of negotiations is expected early next week in Islamabad.