Chicago Sun-Times' Lynn Sweet reports that Illinois Gov. Rod Blagojevich will appoint former Illinois Atty. Gen. Roland Burris to the state's vacant Senate seat at a 3 p.m. ET press conference.

Burris formally announced his interest in the seat two weeks ago, though at that time most expected any appointment would come from Lt. Gov. Pat Quinn. However, Blagojevich remains in office despite facing federal corruption charges, and it's unclear whether Senate leaders will move to keep any Blagojevich appointee from joining the Senate.

Blagojevich and Burris are former political rivals, running against each other for the Democratic nomination in the 2002 gubernatorial race. Blagojevich won with 37% of the vote, with Burris finishing third.

UPDATE: Senate Democratic leaders issued a statement at 2:00 ET urging Blagojevich not to appoint Burris. The statement comes after the 50 Democratic senators sent a letter to Blagojevich on Dec. 10 requesting that he step down as governor and not appoint a successor to the seat. Read the full statement after the jump.

"It is truly regrettable that despite requests from all 50 Democratic Senators and public officials throughout Illinois, Gov. Blagojevich would take the imprudent step of appointing someone to the United States Senate who would serve under a shadow and be plagued by questions of impropriety. We say this without prejudice toward Roland Burris's ability, and we respect his years of public service. But this is not about Mr. Burris; it is about the integrity of a governor accused of attempting to sell this United States Senate seat. Under these circumstances, anyone appointed by Gov. Blagojevich cannot be an effective representative of the people of Illinois and, as we have said, will not be seated by the Democratic Caucus.

"Next week we will start one of the most important debates of the year – outlining an economic recovery plan to create jobs and invest in America. And in the coming weeks, we will be working to protect homeowners and consumers, make America more energy independent, strengthen our national security, and improve health care and educational opportunities. There is much work to do and a lot at stake. It is thus critical that Illinois and every other state have two seated Senators without delay.

“We again urge Gov. Blagojevich to not make this appointment. It is unfair to Mr. Burris, it is unfair to the people of Illinois and it will ultimately not stand. The governor must put the interests of the people of Illinois and all Americans first by stepping aside now and letting his successor appoint someone who we will seat."