WASHINGTON (Reuters) - US Secretary of State Mike Pompeo said his country had credible information that the Iranian oil tanker "Adrian Daria-1" was heading for Syria, while the US Treasury listed the tanker on its blacklist and imposed sanctions on its captain.

Pompeo said on his Twitter account that Iranian Foreign Minister Mohammad Javad Zarif had assured the United Kingdom that an Iranian Revolutionary Guards oil tanker would not be heading to Syria, but the United States had documented information that it was heading to the port of Tartous in Syria.

Pompeo expressed hope that the tanker would change course, noting that it was a big mistake to trust the Iranian minister. Pompeo was accompanied by a photo of the Iranian tanker and a map of Syria, referring to its destination.

The US Treasury Department has also announced sanctions against anyone who supports the Iranian tanker Grace 1, which was held in Gibraltar.

The ban includes all the property and interests of anyone providing support to the Iranian tanker, as well as its assets in the United States, the ministry said.

The Iranian tanker was called Grace 1 and was being held in Gibraltar (Reuters)

Treasury Undersecretary for Terrorism Segal Mandelker said such a tanker, which carries 2 million barrels of oil, enables the IRGC to ship and transport large quantities of oil it tries to conceal and sell illegally to "finance the regime's malicious activities and spread terrorism."

The "Wall Street Journal" has quoted sources described as informed that the Iranian tanker is preparing to transfer its cargo of crude oil in small ships to deliver to Syria, pointing out that this violates the conditions of the tanker's release.

Earlier on Friday, Turkish Foreign Minister Mevlut Cavusoglu said the Iranian tanker was in waters south of Turkey and was heading to Lebanon.

Asked if the tanker was heading for Turkey, Gawishoglu told a news conference in Oslo, "This tanker is not actually heading towards Iskenderun, it is heading towards Lebanon," but without specifying whether Lebanon is its final destination.

For his part, Lebanese Finance Minister Ali Hassan Khalil said that Lebanon has not been informed that the Iranian tanker is moving towards one of the Lebanese ports.

The site "Marine Traffic" to track the movement of ships had shown earlier on Friday that the tanker - which is the focus of a confrontation between the United States and Iran - changed course again and heading to the port of Iskenderun in southeastern Turkey.

The Gibraltar authorities released the Iranian tanker in the middle of this month after being detained for five weeks on suspicion of transporting Iranian oil to Syria in violation of EU sanctions.