US Marines boarded an Iranian-flagged oil tanker in the Gulf of Oman earlier Wednesday as part of ongoing enforcement operations tied to a US maritime blockade.

Marines from the 31st Marine Expeditionary Unit boarded an Iranian-flagged oil tanker suspected of attempting to violate the U.S. blockade by transiting toward an Iranian port, according to US Central Command (CENTCOM).

“U.S. forces continue to fully enforce the blockade and have now redirected 91 commercial ships to ensure compliance,” CENTCOM said.

CENTCOM added that American forces released the vessel after searching and directing the ship’s crew to alter course.

As of May 20, U.S. forces have redirected 90 ships and disabled 4 to ensure compliance.

The military boarded the tanker after US president Donald Trump said he had called off scheduled attack on Iran but instructed the US military to be prepared to go forward with a full, large scale assault of Iran, on a moment’s notice, in the event that an acceptable deal is not reached.

He said he had planned a military attack for Tuesday but put it off, saying America’s allies in the Gulf asked him to wait because they feel they are close to a deal with Iran.