LONDON/NEW YORK (Reuters) – The United States is considering imposing sanctions on at least 40 additional foreign oil tankers for trading with Venezuela, four shipping sources told Reuters on Friday.

The sources said the potential sanctions on the various ships could be imposed imminently, although no decision had been taken yet.

The vessels that could be targeted included 25 supertankers, which can each carry a maximum of 2 million barrels of oil, and 17 smaller vessels, the sources said.

There was no immediate comment from the U.S. Treasury Department. The White House and U.S. State Department did not immediately respond to requests for comment.  

U.S. officials have steadily added tankers and shipping companies to the blacklist over their dealings with Venezuela since Washington imposed sanctions, and have warned that more will be targeted if they fail to abide by sanctions.

Earlier this week the U.S. Treasury said it had imposed sanctions on four shipping firms for transporting Venezuelan oil, the latest escalation in Washington’s effort to oust socialist President Nicolas Maduro by cutting off the OPEC nation’s crude exports.

Washington imposed sanctions on Venezuelan state-run oil company Petroleos de Venezuela in early 2019, shortly after the United States and dozens of other countries accused Maduro of remaining in power illegitimately after a 2018 election that was widely viewed as fraudulent.

Maduro blames the sanctions for Venezuela’s woes and accuses Washington of seeking to oust him in order to control the country’s vast crude reserves.