This report updated Aug. 20, 2019, 3:12 p.m.

WASHINGTON - The United States is warning entities in the Mediterranean against working with an Iranian-flagged oil tanker now sailing through the region after being freed from detention by Gibraltar.

The State Department repeated allegations that the Adrian Darya 1 was "transporting illicit oil to fuel the Iranian regime's and Syrian regime's campaigns of terror and oppression," and it said those who assist it could be considered providing support to U.S.-designated terror organizations.

"We have conveyed our strong position to the Greek government on the matter, as well as ports in the Mediterranean that should be forewarned about facilitating this vessel," it said in a statement Monday.

Brian Hook, the State Department's special representative for Iran, said Tuesday that the U.S. wants to ensure that the oil on the Adrian Darya is not used by Iran's Revolutionary Guard Corps to fund its operations.

"And so, we're tracking its movements, but we're tracking the movements of all Iranian oil tankers," Hook said.

Maritime trackers believe the Adrian Darya is headed to the Greek port of Kalamata, arriving next Sunday, but Athens says it has not received any request for the tanker to dock there.

U.S. Secretary of State Mike Pompeo said the decision by Gibraltar authorities to free the tanker after holding it on suspicion the vessel was taking oil to Syria in violation of European Union sanctions was "unfortunate." He told the U.S. cable network Fox News the eventual sale of the oil on board would benefit Iran's Quds Force.

"If they are successful they will have more money, more wealth, more resources to continue their terror campaign, to continue their assassination campaign. This is what we're trying to stop," Pompeo said.

Iranian Foreign Minister Mohammad Javad Zarif said Iran was being non-committal about the eventual destination of the oil because he said the United States "illegally tries to bully others from purchasing our oil."

He also said that while Iran believes the United States is seeking "more escalation" with Iran, the Islamic Republic is "happy this ordeal (over the oil tanker) has ended and I hope this will lead to less escalation."

Gibraltar denied several U.S. requests to prevent the vessel from leaving the waters of the British territory, and said Iran had given written assurances the oil on board would not be shipped to Syria.

Iranian Foreign Ministry spokesman Abbas Mousavi told reporters Monday that Iran had warned the United States through official channels against making any new attempt to seize the tanker, saying the result would be "heavy consequences."

Mousavi also denied there was a connection between the July 4 detention of the Adrian Darya 1 and Iran's move later last month to seize the British-flagged Stena Impero tanker in the Strait of Hormuz.

British officials have said they saw Iran's action as a reciprocal move.