"With oil prices lower than they were when we announced our sanctions and global production stable, we are on the fast track to zeroing out all purchases of Iranian crude," Hook said.
Earlier, a senior Trump administration official told Reuters on Monday that the US intends to follow through on its policy towards Iran with new sanctions that would target areas of its economy that have not been hit by two packages of sanctions introduced last year.
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One of the potential areas, according to the official, would be changing the existing waivers to eight Iranian oil buyers that had been introduced with the latest sanctions back in November, that would limit oil exports from Iran, the fourth-largest producer in OPEC.