The paper quoted unnamed U.S. intelligence officials as saying Chalabi, an anti-Saddam Hussein Iraqi exile who has now fallen out with Washington, had betrayed "one of Washington's most valuable sources of information about Iran."

It was widely reported last month, after the Bush administration cut off funding for Chalabi's Iraqi National Congress, that Chalabi had provided Iran with American secrets.

But the report published by the New York Times on its Web site on Tuesday gave new details.

The paper said the Bush administration had asked it and other news organizations to delay publication of the specifics, citing national security concerns. But the administration withdrew the request on Tuesday, the Times said.

"American officials said that about six weeks ago, 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," The Times said.

It said the Iranian official in Baghdad then sent a cable to Tehran, using the broken code and describing his conversation with Chalabi.

"That encrypted cable, intercepted and read by the United States, tipped off American officials to the fact that Chalabi had betrayed the code-breaking operation," the paper said.

It said that according to the cable, Chalabi had received the information about the code from a "drunk" American.

The paper said the FBI was trying to establish exactly what information Chalabi had given to the Iranians and who told him that the code had been broken.