CHIPPEWA FALLS, Wisc. — The U.S. military said it shot down four Iranian drones that were launched toward the Strait of Hormuz on Friday and then struck some of the Islamic Republic’s coastal surveillance radar sites in response, raising the risk to a shaky ceasefire as the Trump administration ramps up pressure on Iran.

“The attack drones posed an immediate threat to regional maritime traffic,” U.S. Central Command said on social media.

The military is enforcing a blockade on Iranian ports in response to Tehran’s chokehold on the crucial corridor for global oil and natural gas shipments, which has sent energy prices spiking and posed political problems for President Donald Trump’s Republican Party ahead of the midterm congressional elections.

U.S. Central Command said it hit the radar sites, including an island in the strait, “to defend against further attacks.”

It was the latest in back-and-forth attacks that have strained the tenuous ceasefire in the war and efforts to reach a deal to extend that truce. Earlier this week, Iranian drones heavily damaged a passenger terminal at Kuwait’s main airport, killing one person, wounding dozens and briefly closing the airfield.

Despite the attacks raising new concerns that the ceasefire could collapse, Trump told reporters Friday that “the situation with Iran seems to be going quite well.”

“We’re going to come out of Iran very quickly and it’s going to be very strong one way or the other, whether it’s a piece of paper or the very tough way,” Trump said at an event with farmers in Wisconsin.