The Chicago Sun-Times' Lynn Sweet is reporting that Obama will have a conference call with supporters at 11am Chicago time to announce plans for a 2008 run for the White House.

Supporters of Sen. Barack Obama (D-Ill.) are being told this morning there will be an 11 a.m. Chicago time conference call. Expected to be discussed is Obama filing papers to officially launch his 2008 White House run. Obama is expected to hit the road to travel to early primary states in the coming days.

The call is being organized by Nate Tamarin, who was the political director for Obama's Washington D.C. based political action committee the Hope Fund. He now works with Pete Giangreco, the founder of the Strategy Group in Evanston, expected to handle Obama's direct mail in the 2008 campaign.

The Chicago Tribune's Mike Dorning suggests a public announcement may come Wednesday on Oprah:

Speculation has been building that an announcement on Obama's presidential intentions in imminent.

Speaking to reporters outside St. Mark Cathedral in Harvey on Monday, Obama said an announcement was coming "very soon."

Oprah Winfrey's web site also is curiously silent on the subject of her show this Wednesday. Obama has previously indicated he may make an announcement on a presidential campaign on her highly rated television talk show.