Destroyers to 'accompany' US flagged ships through the Straights of Hormuz.

USA Today:

The Navy will accompany ships in and around the Persian Gulf following threats and harassment from Iranian patrol boats, a Defense Department official said Thursday.

The Navy has four ships in the Gulf and the Strait of Hormuz, a busy shipping lane for commercial cargo vessels. The warships will not escort individual cargo ships, the official said. Instead, the Navy will maintain communication with the ships while they are in the area and respond to distress calls.

Tensions have grown in the last few weeks between the United States and Iran. Last week, Iranian Revolutionary Guard patrol boats encircled a U.S. cargo vessel there in a "threatening" manner, according to the Defense official who spoke on condition of anonymity because the person was not authorized to speak about that incident or the new Navy order.
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The Navy's new policy is a looser form of maritime protection than an escort, according to a Navy official who was not authorized to describe the tactic publicly. Escorts generally operate within sight of the ships they are protecting, anywhere from one to 10 miles. Accompanying another ship means they remain in radio contact but remain farther away.
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The US does not trust Iran to allow ships to navigate in the region but apparently trust them to honor a nuclear agreement.  Go figure.