The United States, on Wednesday, deployed three Navy fast patrol craft to join the destroyer Farragut in the Straits of Hormuz where Iran seized a cargo ship registered in the Marshall Islands, reports Military.com, quoting a Pentagon spokesman.

“What they’re doing is keeping an eye on things,” Col. Steve Warren, a Pentagon spokesman, said on Wednesday in reference to the U.S. Navy presence in the Straits, adding that the ships are prepared if a response is warranted to ensure safe passage between the Persian Gulf and the Arabian Sea, a heavily trafficked area.

The U.S. “will be able to respond if a response is required,” said Warren, Fox News reports, adding that he was vague when asked to elaborate on how far the United States is willing to go if tensions escalate.

“These [U.S. military] assets give commanders options,” the spokesman told Pentagon reporters, adding that he did not know “what the possibilities are.”

Warrant noted that the U.S. is currently engaged “in discussions with the Marshall Islands on the way ahead.”

He explained that the takeover of the Marshall Islands-flagged MV Maersk Tigris on Tuesday followed a separate harrassment incident last week by Iranian Revolutionary Guard speedboats.

“On April 24, four of the Iranian craft came astern of the MV Maersk Kensington in the Persian Gulf. The Iranian craft followed the Maersk Kensington closely for 15-20 minutes before backing off,” Warren said, according to Military.com.

That incident was reported to U.S. Central Command by the master of the Maersk Kensington.

“It’s difficult to know why the Iranians are acting this way,” declared Warren.

Iran is a state-sponsor of terrorism. The Republic of the Marshall Islands, a former territory of Japan, is a close voting ally of the U.S. and Israel at the United Nations.

Various media outlets reported that Pentagon lawyers determined on Tuesday that the U.S. had no obligations to abide by a treaty obligation to protect the Marshall Islands.

“The Marshall Islands signed a Compact of Free Association with the United States in 1983 and gained independence in 1986 with the Compact’s entry into force,” reads a State Department fact sheet on the U.S.-Marshall Islands bilateral relationship. “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.”

On Tuesday, members of the Iranian Revolutionary Guard reportedly boarded the Marshall Islands-flagged MV Maersk Tigris after Iranian speedboats fired warning shots.

Iran claims the cargo ship crossed into its territorial waters.

The Pentagon said the Maersk Tigris and its 24 member crew are anchored between Iran’s Larak Island and Bandar Abbas, an Iranian port.

Danish shipping giant Maersk said Wednesday that the crew of the Maersk Tigris were safe and “in good spirits,” reports Al Arabiya.