WASHINGTON - The United States has conveyed its "strong position" to the Greek government about an Iranian tanker that sailed for Greece on Monday after it was freed from detention off Gibraltar and Washington says is carrying oil to Syria, a State Department official said.

Any efforts to assist the tanker could be considered as providing material support to a U.S.-designated foreign terrorist organization, which has immigration and potential criminal consequences, the official said.

(Reporting by Lesley Wroughton; Writing by Mohammad Zargham) ((mohammad.zargham@thomsonreuters.com;))