Rezko has been among the Democratic governor's top fundraisers and advisers and can provide prosecutors with a penetrating glimpse into the workings of Blagojevich's inner circle. He was convicted in June of scheming to squeeze companies seeking state business for payoffs.

There were signs that Rezko's relationship with prosecutors had soured in recent weeks. But on Tuesday, both sides agreed to postpone his sentence indefinitely, a sign that prosecutors think their sometimes reluctant witness has more to tell them.

While Rezko squared things with federal prosecutors, attorneys for former Blagojevich campaign chairman Christopher Kelly said he intends to plead guilty to tax charges next month. Among other things, Kelly, a roofing contractor and consultant, is charged with using company funds to pay gambling debts and in at least one case writing the payment off as a business expense.

Kelly could also give the government an inside look at the workings of the Blagojevich administration. But chief defense counsel Michael Monico said Tuesday that "cooperation isn't part of the agreement" under which Kelly will plead guilty.