Brian Hook, who heads the United States State Department’s Iran Action Group, has contacted about a dozen captains of Iranian oil tankers in recent months, offering millions of dollars to pilot their ships to countries that would impound the vessels on behalf of the US, according to a Wednesday report by the Financial Times.

One of those ships was the Adrian Darya 1, also known as Grace 1, which was seized by the British in Gibraltar and has been sailing in the eastern Mediterranean since its release, despite US effortst to the contrary. In response to the FT story, Iranian Foreign Minister Mohammad Javad Zarif tweeted, “Having failed at piracy, the US resorts to outright blackmail — deliver us Iran’s oil and receive several million dollars or be sanctioned yourself.”