Until last month, Chalabi's INC was being paid $340,000 per month out of secret Defense Department intelligence funds for "information collection."

Officials of the NSA and DIA declined to comment. But law-enforcement sources confirmed that the FBI has opened an investigation into the codebreaking leak. The investigation will look into whether Chalabi or his group supplied information about U.S. codebreaking efforts to the Iranians. But, given that Chalabi is not a U.S. citizen and does not have a U.S. security clearance, the more critical issue for investigators will be to find out who in the U.S. government might have leaked such highly sensitive information to Chalabi and the INC, some officials say. Law-enforcement sources indicated that the American investigation will likely focus on whether sensitive information might have been leaked to Chalabi by officials in either the Pentagon or the U.S. Coalition Provisional Authority in Baghdad.

Chalabi and some of his supporters in Washington have insisted that not only did he not compromise U.S. intelligence information by leaking it to Iran but that neither he nor his routine U.S. contacts had access to such tightly guarded American secrets. Chalabi's supporters claim that the Iranian leak investigation is simply being used by Chalabi's enemies in the U.S. bureaucracy--particularly at the State Department and CIA--as an excuse to have him sidelined from the Iraqi political process. They see the related FBI investigation as an excuse for a "witch hunt" against Chalabi supporters inside the administration and in the Pentagon in particular.

Administration officials are treating the allegations with deadly seriousness, however. In remarks to reporters today, White House national-security adviser Condoleezza Rice acknowledged: "Now, it's no secret that the relationship with Ahmad Chalabi has been somewhat strained of late." President Bush also distanced himself from Chalabi, saying he had only met the Iraqi very briefly a few times.

U.S. officials say the investigations into Chalabi's activities may have a long way to go. In addition to the inquiry into the leak of classified information to Iran, Chalabi and the INC are under investigation for corruption by Iraqi authorities, who last month staged a raid on his home and office in Baghdad, and last weekend drove INC personnel out of a satellite office in the Iraqi provinces.

One Bush administration official said that in addition to harboring suspicions that Chalabi had been leaking sensitive U.S. information to Iran both before and after the U.S. invasion of Iraq, some U.S. officials also believe that Chalabi had collected and maintained files of potentially damaging information on U.S. officials with whom he had or was going to interact for the purpose of influencing them. Some officials said that when Iraqi authorities raided Chalabi's offices, one of the things American officials hoped they would look for was Chalabi's cache of information he had gathered on Americans.