Iran seized two United States Navy patrol boats and 10 crew members who were described as “trespassing” on Tuesday in Iranian waters near a major naval base.
But the Pentagon and the State Department said
that one of the boats had experienced mechanical problems while en route from Kuwait to Bahrain on a routine mission. Administration officials said that the military had lost contact with the boats before they strayed into Iranian territorial waters. They said they had received assurances from Iran that the 10 sailors would be returned soon, perhaps on Wednesday.
But a spokesman for the Islamic Revolutionary Guards Corps, Brig. Gen. Ramezan Sharif, was quoted Wednesday morning in the Iranian news media as saying that talk of an immediate release was “speculation.” He said an “investigation” was underway and that “talks” were being held with the sailors, suggesting that they were being interrogated.

The semiofficial Fars news agency in Iran said that the boats had illegally traveled more than a mile into Iranian waters near Farsi Island, the site of a major Iranian naval base. It said that members of the Islamic Revolutionary Guards Navy had confiscated GPS equipment, which would “prove that the American ships were ‘trespassing’ around in Iranian waters.”

The waters where the boats were sailing are a frequent location for intelligence collection by the United States, Iran and many gulf countries. The American and Iranian navies encounter each other frequently there.
The detention of the sailors comes at a particularly delicate moment in the tense American-Iranian relationship, just days before the formal implementation of a nuclear deal in which the United States is supposed to unfreeze about $100 billion in Iranian assets.
That step is to be made after international nuclear inspectors verify that Iran has shipped 98 percent of its nuclear fuel out of the country and disabled and removed centrifuges, and taken a large plutonium reactor permanently offline.
The American sailors were aboard two riverine patrol boats — 38-foot, high-speed boats that are used to patrol rivers and littoral waters. One official said the two vessels, which often patrol shallow waters near Bahrain, had failed to make a scheduled rendezvous with a larger ship to refuel.
Secretary of State John Kerry, an official said, was notified of the seizing of the sailors while meeting with top Philippine officials and Defense Secretary Ashton B. Carter. Mr. Kerry broke off the meeting and called his Iranian counterpart, Mohammad Javad Zarif, with whom he spent months negotiating the nuclear accord. As he walked into the House chamber Tuesday night for President Obama’s State of the Union address, Mr. Kerry said the sailors were “going to get out.”
It is unclear what power Mr. Zarif may have to intervene. Many American and Middle Eastern officials believe that recent actions by the Iranian Navy against American forces in the gulf may be intended to embarrass Mr. Zarif and President Hassan Rouhani. The Islamic Revolutionary Guards Corps was responsible for the military side of the nuclear program, and many of its senior officers have objected to the nuclear agreement.
The Navy’s Fifth Fleet maintains a presence in the Persian Gulf, including the aircraft carrier, and lately has had several episodes with Iran.

Two weeks ago, the Iranian Navy harassed an American carrier and a French frigate in the Strait of Hormuz, launching rockets that passed within 1,500 yards of the aircraft carrier Harry S. Truman.
Last year in the Gulf of Aden, an Iranian Navy frigate approached a ship where an American military helicopter had just landed and pointed a heavy machine gun at the copter for several minutes before turning around, all while an Iranian film crew videotaped the encounter. The Fifth Fleet, for its part, has its own videotape of the episode.

In 2007, the Revolutionary Guards Navy captured 15 British military service members and held them for 13 days, making a point of protecting its sea borders. A year later, the British Navy released a report saying that its vessels had been in an area with disputed borders between Iran and Iraq.