An Iranian supertanker left Gibraltar late Sunday after the territory rejected a U.S. request to continue holding the ship in a detention on suspicion of attempting to breach global sanctions against Syria.

The tanker set sail late Sunday, according to a marine traffic monitoring site and Gibraltar news outlets. The Gibraltar government, in a statement, cited differences between the sanctions authorized by the United States and those of the European Union.

"The European sanctions regime against Iran, which is applicable in Gibraltar, is much narrower than that applicable in the U.S.," said the statement from Gibraltar, a British territory.

Hamid Baeidinejad, Iran's ambassador to the United Kingdom, said the ship could depart within hours after the rejection was announced. Tehran said it was ready to dispatch a fleet to escort the tanker if necessary.

"The era of hit and run is over," said Iran's navy commander, Rear Adm. Hossein Khanzadi.

The U.S. State Department did not immediately respond to a request from USA TODAY for comment.

The ship, containing more than 2 million gallons of Iranian light crude oil, was seized July 4 in a British Royal Navy operation off the coast of Gibraltar. The seizure aggravated fears of a conflict in the Persian Gulf, where Iran claims control of the Strait of Hormuz, a strategic waterway for oil shipments.

After Gibraltar's detention of the Iranian tanker, then known as Grace 1, Iran seized the British-flagged oil tanker Stena Impero as it passed through the Strait of Hormuz. The Islamic Republic is still holding the British vessel, claiming it failed to stop after colliding with an Iranian fishing boat.

Dispute deepens:U.S. issues warrant to seize Iran oil tanker 'Grace 1' after Gibraltar judge orders its release

Iran has seized other foreign oil tankers in recent months – and downed a U.S. surveillance drone, raising the ire of President Donald Trump.

Iran denies the Grace 1 was headed to Syria and accused the British of "maritime piracy." A court in Gibraltar ordered the tanker released Thursday, setting off a flurry of diplomatic and legal efforts to keep the ship from leaving.

On Friday, the U.S. Justice Department issued a warrant to seize the tanker for forfeiture, claiming the Iranians illegally used the U.S. banking system to finance the shipment of oil to Syria.

Secretary of State Mike Pompeo also warned mariners against signing on to ships linked to the Islamic Revolutionary Guard Corps or others under U.S. sanctions.

"The maritime community should be aware that the U.S. government intends to revoke visas held by members of such crews,” Pompeo said.

Tanker seized:Iran seizes another foreign oil tanker, state media says

The Gibraltar government noted that the Revolutionary Guard is not a designated foreign terrorist organization in Gibraltar, the U.K. or in most of the EU generally, unlike in the U.S.

The weeks-long diplomatic dispute between Tehran and Washington comes amid a standoff between the two countries after Trump withdrew from an international nuclear accord with Tehran and reimposed sanctions.

Tensions in the Persian Gulf have been on the rise since. Some European leaders have been unwilling to follow the U.S. lead in attempting to isolate the Persian nation.

Contributing: Kim Hjelmgaard and Kristin Lam, USA TODAY; The Associated Press