Iranian military forces seized two U.S. Navy boats Tuesday and are detaining them on Iran's Farsi Island in the Persian Gulf, senior U.S. officials told NBC News.
The 10 American sailors were on a training mission around noon ET when one of the boats may have experienced mechanical failure and drifted into Iranian-claimed waters, officials said. Iran's coast guard took them into custody.
The officials said it's unclear whether the sailors — nine men and one woman — aboard the two small riverine vessels had strayed into Iranian territorial waters before they were captured. NBC Special Report: U.S. Ships Held by Iranian Forces 2:12
"At this point, we're still monitoring the situation and it's not entirely clear what happened," White House spokesman Josh Earnest said on MSNBC, adding that Iranian authorities confirmed that the sailors are safe.
Earnest said there remained no exact time frame for when the sailors would be let go, but didn't expect a long delay.
Related: Iran Attacks Replica U.S. Warship in Strait of Hormuz Missile Drill
Following reports of the incident, Secretary of State John Kerry spoke with Iranian officials in Tehran by phone, attempting to secure the sailors' release.
One senior official told NBC News the Iranians understand it was a mistake and have agreed to release the Americans in international waters within hours.
The Persian Gulf has been a flash point in the Middle East, and the incident comes on the same day President Barack Obama is set to give his annual State of the Union address. Image: Coastal Riverine Squadron 3 operations Riverine Command Boat (RCB) 802, assigned to Combined Task Group (CTG) 56.7, conducts patrol operations in the Arabian Gulf in Oct. 2015. Two small riverine vessels of this type were detained on Iran's Farsi Island. MC2 Torrey W. Lee / U.S. Navy
Senior U.S. military commanders also criticized Iran last month for its "highly provocative" actions when it fired unguided rockets near U.S. ships, including the USS Harry S. Truman aircraft carrier.
Pentagon spokesman Peter Cook told The Associated Press that the boats were moving between Kuwait and Bahrain when U.S. officials lost contact with them. Farsi Island sits in the Persian Gulf in between Iran and Saudi Arabia, and is fortified by Iranian Revolutionary Guards.
Related: U.S. Carrier Harry S. Truman Has Close Call With Iranian Rockets
"We have been in contact with Iran and have received assurances that the crew and the vessels will be returned promptly," Cook said.
Retired Army Gen. Barry McCaffrey, an NBC News military analyst, said the seizure of American boats is "very bad news" and highlights how the Navy may have failed to have surveillance on its vessels.
"We simply can't allow ground, air or naval units to be seized by a foreign hostile power," McCaffrey said on MSNBC. "I hope they're back real quickly. This is an affront to our military presence in the Gulf and will unsettle our allies in the region."
Sen. Barbara Boxer, D-Calif., said on MSNBC that the pending release of the sailors shows how diplomacy between U.S. and Iranian officials "is working."
"Hopefully this will be resolved, and it won't be an issue that we're talking about in a couple of hours," she said.
This is NOT good. Remind anyone that Obama = Jimmy Carter II ??
