The decision carried in the U.S. government's official journal, the Federal Register, and confirmed by the State Department, is the most sweeping sanctions action to date under the Iran Nonproliferation Act approved by Congress in 2000.

In all, 14 firms or individuals, seven from China, two from India and one each from Russia, Belarus, Ukraine, North Korea and Spain, were hit with sanctions barring them from doing business with the U.S. government or buying U.S. high-tech equipment for two years.

The decision brought to 23 the number of foreign entities sanctioned under the four-year-old law aimed at curbing sales of cruise and ballistic missile equipment and know-how and weapons of mass destruction technology to Iran.

Several of the firms identified Wednesday have been cited for violating U.S. export laws before, including China's North Industries Corporation, NORINCO, and the Changgwang Sinyong Corporation of North Korea, which is the export outlet for that country's military establishment.

At a news briefing, State Department spokesman Richard Boucher said companies with repeated violations will be subject to successive two-year sanction terms.

"In many cases the imposition of successive sanctions, one on top of the other, the main effect is to extend the period of time that entity would be subject to sanctions for," he said. "But it is a requirement of law that we make these determinations, and impose sanctions. And somebody who has been doing something more recently deserves to suffer the consequences for a longer period of time."

The Spanish firm cited, Telstar, is understood to be the first company from a U.S. NATO ally to face penalties under the Iran Nonproliferation Act.

Mr. Boucher would not give specific information on equipment and technology that may have reached Iran in violation of the law.

The sanctions apply only to companies and individuals and not their host governments, except in the case of North Korea, where the company cited is effectively part of that government.