WASHINGTON—Iran began a major naval exercise near the Strait of Hormuz Thursday, in an apparent response to rhetoric from President Donald Trump in recent days that he would ratchet up pressure against Tehran, U.S. defense officials said.
The U.S. believes the exercises “fully started” Thursday, one defense official said, and could continue until Aug. 6. A second official said there are more than 100 boats and ships participating in the exercise, but most are considered smaller craft.
On Thursday, the U.S. saw boats going in and out of port, the first defense official said.
An air component, consisting primarily of unmanned aerial vehicles, or UAVs, are also are participating in the exercise, a military official said. Iranian officials didn’t respond to a request for comment.
President Trump, in a July 22 Twitter post written in capital letters, warned of dire repercussions if Iran threatened the U.S.
“NEVER, EVER THREATEN THE UNITED STATES AGAIN OR YOU WILL SUFFER CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE,” Mr. Trump wrote.
The annual exercise appears to have been moved up on the Iranian calendar by several days, reinforcing the view that it is a response to Mr. Trump’s recent comments.
Some officials in the U.S. military believe the Iranians are simply trying to send a message that if Tehran wanted to close the Strait of Hormuz, a critical shipping route that links the Persian Gulf with the Arabian Sea and ultimately, the Indian Ocean, it could do so.
“We’re watching it pretty closely,” said a military official.
On Monday, during a press conference with Italian Prime Minister Giuseppe Conte, Mr. Trump appeared to extend an olive branch to Iran, saying he would meet its leaders with “no preconditions.” Iran rejected that proposal.
The U.S. naval presence in the region currently is somewhat below levels that have been considered normal for the area in recent years.
There is no aircraft carrier strike group after the USS Harry S. Truman left the region last month. In recent weeks, the most prominent U.S. naval presence in the Middle East was the amphibious warship Iwo Jima, which arrived in the Persian Gulf last month and has since left.
Last month, the U.S. Navy quietly deployed the three-ship Essex Amphibious Ready Group and the 13th Marine Expeditionary Unit, which will operate in both the Middle East and the Western Pacific.
Write to Gordon Lubold at Gordon.Lubold@wsj.com and Nancy A. Youssef at nancy.youssef@wsj.com