(JNS) An Iranian oil tanker freed by the United Kingdom sailed for Greece earlier this week, as Washington denounced its release from Gibraltar, and warned Athens and Mediterranean ports against assisting the ship.

“It’s unfortunate that that happened,” U.S. Secretary of State Mike Pompeo told the Fox News Channel regarding the Grace 1’s release. The United States made an unsuccessful last-minute attempt to stop the freeing of the tanker.

Iran said if the United States attempts to seize the ship, there would be “heavy consequences.” Iranian Foreign Minister Mohammad Javad Zarif said that the United States is seeking “more escalation.”