WASHINGTON — Small Iranian fast boats swarmed around American warships in the Persian Gulf, and a man speaking heavily accented English threatened, “I am coming to you. … You will explode after … minutes,” according to a video released yesterday by the Pentagon.

The Iranian boats appeared to ignore repeated warnings from the American ships, including horn blasts and radio transmissions.

In a four-minute, 20-second video, shot from the bridge of the destroyer USS Hopper, the small boats — including a bright blue one — can be seen racing near the wake of the American ships and crossing close to each other.

From the Hopper’s bridge, after spotting the approaching Iranian boats, a Navy crew member says over the radio: “This is coalition warship. I am engaged in transit passage in accordance with international law. Intend no harm.”

Often uneven and shaky, the video condenses what Navy officials have said was a 20-minute or so clash. It ends with a blank screen, as only the audio of the Navy’s final warning can be heard, just after the voice warns that they are coming.

“Inbound small craft: You are approaching a coalition warship operating in international waters. Your identity in unknown; your intentions are unclear,” the unidentified crew member says. He then cautions the Iranians that if they do no steer clear they will be “subject to defensive measures.” “Request that you alter course immediately to remain clear,” the crew member says.