The United States was grappling Wednesday with a naval dilemma: How should the Navy respond to Iranian ships intercepting a civilian container ship in the Strait of Hormuz and holding if the vessel wasn’t flying the U.S. flag?

The Maersk Tigris was flagged by the Marshall Islands when it was intercepted Tuesday, said Col. Steve Warren, a Pentagon spokesman. The tiny Pacific nation was seized by the U.S. military during World War II and gained independence in 1986. The government there signed a legal agreement with Washington in 1983 known as a Compact of Free Association that guides their relations, and requires the United States to respond militarily on behalf of the Marshall Islands when required.

“The United States has full authority and responsibility for security and defense of the Marshall Islands, and the Government of the Marshall Islands is obligated to refrain from taking actions that would be incompatible with these security and defense responsibilities,” according to a State Department fact sheet.

What that means is up for debate. There is little, if any, precedent for the United States in meeting those obligations during a standoff like this.

Warren said Wednesday that the guided-missile destroyer USS Farragut, dispatched Tuesday after the Maersk Tigris issued a distress call, is now in the vicinity of the container ship along with the patrol boats USS Thunderbolt, USS Firebolt and USS Typhoon. They are in “close enough proximity to Maersk Tigris that they will be able to respond if a response is required,” Warren said.

U.S. and Marshallese officials are in discussions on how to react, Warren said. But the actions are considered provocative: The container ship was in Iranian waters when it was intercepted, but traveling a widely accepted international shipping lane in what is considered one of the world’s most significant naval choke points.

Warren said he wasn’t sure if the Farragut is within view of the Maersk Tigris, but the Navy vessel carries helicopters that could be used to observe it.

The incident comes just after the United States and Iran avoided a confrontation near Yemen. Pentagon officials said Friday that Iranian vessels possibly carrying weapons to Houthi rebels in the Yemeni port of Aden had turned back to the Persian Gulf, prompting the aircraft carrier USS Theodore Roosevelt to do the same.

Iranian Foreign Minister Javad Zarif told a crowd in New York on Wednesday that Tehran still respects freedom of movement in the Persian Gulf. The ship was required to pay damages based a court order out of a legal case that had been ongoing for 14 years, Zarif said, according to Reuters.

The crew of the ship is in good spirits, the company reported. Warren said he did not know whether they were still aboard the ship, or had been taken ashore.