A report by Bloomberg says that a British oil tanker is staying in the Persian Gulf in fear of being seized by Iran in retaliation for an Iranian tanker impounded by the British and Gibraltar authorities since July 4.

The mid-size oil tanker capable of carrying one million barrels of oil was reportedly moving toward one of Iraq’s oil terminals when it changed course and is currently anchored close to Saudi Arabia.

The decision to keep the tanker, The British Heritage outside the reach of the Iranian navy was made by British Petroleum, according to the report.

Iran’s defense minister General Amir Hatami on Monday threatened retaliation against Britain, following threats by two other influential Iranians last week.

Tehran has been in diplomatic contact with UK and the British ambassador has visited the Iranian foreign ministry twice since the arrest of the tanker Grace 1 at Gibraltar.

Tehran has called the British action “piracy” and against “international norms”.

The tanker Grace 1 was stopped by Gibraltar authorities with the assistance of Royal Marines on suspicion of carrying around two million barrels of fuel oil to a refinery in Syria, which is under European Union sanctions.

The U.S. has voiced satisfaction at the British interdiction, but Gibraltar has denied it took the action at the behest of the United States.