The Obama administration on Tuesday clarified how it would enforce recently passed Iran sanctions legislation, including how the United States would determine if another country has significantly reduced oil purchases from Iran.

We are working intensively to implement the (National Defense Authorization Act's) financial sanctions as part of our broad-based efforts to stop Iran's illicit nuclear activities, David Cohen, U.S. Treasury under secretary for terrorism and financial intelligence, said in a statement.

We urge banks worldwide to quickly terminate their ties to the Central Bank of Iran, both to protect themselves from CBI's illicit financial activities and to isolate the CBI from the international financial system, he said.

(Reporting by Doug Palmer; Editing by Leslie Adler)