The US and the Marshall Islands are trying to figure out how to get back a cargo ship the Iranian navy detained in the Strait of Hormuz

Iran NavyREUTERS/Fars News/Hamed JafarnejadIranian military personnel participating in the Velayat-90 war game on Sea of Oman near the Strait of Hormuz in 2011.

Officials from the United States and the Marshall Islands are discussing “the way ahead” after Iranian patrol boats forcibly diverted a cargo ship flying a Marshall Islands flag into an anchorage in Iranian waters, the Pentagon said on Wednesday, according to Reuters.

A US Navy destroyer, the Farragut, and three coastal patrol ships, the Thunderbolt, Firebolt and Typhoon, were operating in the vicinity of the Strait of Hormuz conducting maritime security operations following the detention of the cargo ship, the MV Maersk Tigris, the Pentagon said.

Army Colonel Steve Warren, a Pentagon spokesman, said US forces also had reconnaissance aircraft in the area to monitor developments with the Maersk Tigris, which was forcibly diverted to an anchorage near the port of Bandar Abbas as it was travelling through the Strait of Hormuz on Tuesday.

Warren said the Pentagon was not clear why the ship was detained because Iran had given differing explanations for its rationale.

The Maersk Tigris was approached by Iranian Revolutionary Guard patrol boats on Tuesday while traversing the strait and was ordered to proceed into Iranian territorial waters. When the ship’s master declined, the patrol boats fired across the ship’s bow, forcing it to comply.

The vessel was later boarded by Iranian forces.

It was the second ship in less than a week to be approached by Iranian patrol boats. The earlier vessel, the US-flagged Maersk Kensington, was followed but no shots were fired.

Warren said the incidents showed a pattern of harassment.

“It has certainly created a situation where maritime cargo vessels presumably would have to consider the risks of traversing the strait,” he told reporters.

Warren said the US government was in discussions with the Marshall Islands and referred reporters to the State Department. The United States is responsible for defence of the islands under an association compact that has been in force since 1986.

However, US officials have privately told Reuters that the United States is under no legal obligation to respond militarily in the case of the detained cargo ship.

And it’s unlikely that the US will go out of its way to recover the vessel.

Screen Shot 2015 04 29 at 2.09.57 PMGoogle MapsPosition of the Marshall Islands

Like thousands of other ships around the world, the Maersk Tigris flies the flag of the Marshall Islands without having much of a connection to the place. It’s only registered in the islands, which have around 70,000 residents and are over 4,500 miles southeast of the US, in order to take advantage of the country’s favourable taxation and regulatory regime.

According to the UN’s 2014 Review of Maritime Transport, 2,207 Marshall Islands-flagged vessels were responsible for 9.1% of the world’s dead-weight tonnage in 2014, giving the islands the fourth-largest merchant fleet on earth, and third-largest in tonnage.

Over 99% of Marshall Islands-flagged vessels were foreign-owned. The Marshall Islands does not tax revenues from foreign-owned ships that are registered in the country and has “balanced rules and regulations” regarding mortgaging a commercial ship, according to a fact sheet from the consulting firm Norton Rose Fulbright.

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