The Bush administration, citing national security concerns, asked The New York Times and other news organizations not to publish details of the case. The Times agreed to hold off publication of some specific information that top intelligence officials said would compromise a vital, continuing intelligence operation. The administration withdrew its request on Tuesday, saying information about the code-breaking was starting to appear in news accounts.

http://www.nytimes.com/2004/06/02/politics/02CHAL.html?hp=&pagewanted=all&position=

Mr. Chalabi and his aides have said he knew of no secret information related to Iran and therefore could not have communicated any intelligence to Tehran.

American officials said that about six weeks ago, Mr. Chalabi told the Baghdad station chief of Iran's Ministry of Intelligence and Security that the United States was reading the communications traffic of the Iranian spy service, one of the most sophisticated in the Middle East.

According to American officials, the Iranian official in Baghdad, possibly not believing Mr. Chalabi's account, sent a cable to Tehran detailing his conversation with Mr. Chalabi, using the broken code. That encrypted cable, intercepted and read by the United States, tipped off American officials to the fact that Mr. Chalabi had betrayed the code-breaking operation, the American officials said.

The Iranians sent what American intelligence regarded as a test message, which mentioned a cache of weapons inside Iraq, believing that if the code had been broken, United States military forces would be quickly dispatched to the specified site. But there was no such action.

The F.B.I. has opened an espionage investigation seeking to determine exactly what information Mr. Chalabi turned over to the Iranians as well as who told Mr. Chalabi that the Iranian code had been broken, government officials said. The inquiry, still in an early phase, is focused on a very small number of people who were close to Mr. Chalabi and also had access to the highly restricted information about the Iran code.