U.S. forces launched an effort to guide commercial ships through the Strait of Hormuz on Tuesday, with the first two ships, both American-flagged merchant vessels, sailing through unscathed. Joint Chiefs Chairman Dan Caine said the safety corridor in the key waterway for oil and gas transport involves guided-missile destroyers, more than 100 aircraft and 15,000 service members.

Defense Secretary Pete Hegseth and Joint Chiefs of Staff chair Gen. Dan Caine held a news conference at 8 a.m. EDT. Watch it in our video player above.

Defense Secretary Pete Hegseth said the forces prefer a peaceful effort to "guide" the more than 22,500 mariners stuck on more than 1,550 vessels out of the Persian Gulf, but are ready if needs change. "This is a temporary mission for us," Hegseth said. "We expect the world to step up." Iran has denounced the move as a ceasefire violation.

READ MORE: Iran war's fragile ceasefire tested in U.S. attempt to open the Strait of Hormuz

It is unclear what will follow. The U.S. Central Command said Iran earlier launched multiple cruise missiles, drones and small boats at civilian ships under the U.S. military's protection, and that U.S. helicopters sank six small boats involved in the attacks. It denied Iranian reports that American vessels had been struck.

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Joint Chiefs Chairman says Iran attacks do not necessarily mean they violated ceasefire

Caine told reporters at the Pentagon on Tuesday that Iran's recent acts of aggression are below the threshold of "major combat operations."

That means Tehran, in the Trump administration's view, has not violated the tenuous ceasefire between the U.S. and Iran.

WATCH: U.S. and Iran truce tested over the Strait of Hormuz, threatening to reignite conflict

"Since the ceasefire was announced, Iran has fired at commercial vessels nine times and seized two container ships, and they've attacked U.S. forces more than 10 times – all below the threshold of restarting major combat operations at this point," Caine said.

The administration has cited the ceasefire in asserting that the president does not have to give a formal update to Congress on the war under the War Powers Resolution. That law typically requires presidential updates on war activities 60 days after beginning military action.

Caine lays out U.S. forces manning Strait of Hormuz

Saying that more than 100 U.S. military aircraft are patrolling the skies "24 hours a day," Caine said Tuesday marked a "quieter" period in the Strait.

Caine added that there were 22,500 mariners on more than 1,550 vessels in the Persian Gulf, unable to transit.

WATCH: Analyzing the U.S. effort to reopen the Strait of Hormuz amid tensions

He went on to commend the troops of the 82nd Airborne Division, who he said were using "next generation tactical networks" to "seamlessly synchronize" efforts in support of military activity.

Hegseth also says ceasefire is not over

The defense secretary confirmed that the ceasefire remains in effect despite some Iran strikes and the ongoing U.S. blockade.

"No, the ceasefire is not over," Hegseth said, reaffirming Caine's earlier statements.