David Kay — a former U.S. adviser in Iraq — spent months questioning Tariq Aziz and others. He says Aziz quickly turned on Saddam and could testify at any trial. "He talks about direct orders to murder, to assassinate, to kill," says Kay. NBC News has learned U.N. investigators probing corruption in the U.N. oil for food program were scheduled to question Aziz last week. That session was delayed for security reasons. The U.N. investigation — led by former Federal Reserve chairman Paul Volcker — is looking into Saddam's alleged diversion of oil money that was supposed to go for food to U.N. officials and politicians in key countries. U.S. officials say Aziz already has implicated the French and others, claiming payoffs were made with the understanding that recipients would support Iraq on key matters before the U.N. "He pointed to specific individuals in Russia and France, in the United States — that received favorable treatment," says David Kay. Now, sources tell NBC News that Aziz has indicated he's finally ready to talk about alleged bribes to U.N. officials. U.N. investigators refuse to comment.