CHICAGO — Illinois U.S. Senate appointee Roland Burris is leaving for Washington this afternoon for a high-stakes showdown on Capitol Hill about whether he'll succeed President-elect Barack Obama in Congress.

Burris, appointed by embattled Gov. Rod Blagojevich, was leaving a day after dozens of black leaders and ministers organized by U.S. Rep. Bobby Rush gave him a rousing send-of at New Covenant Church on Chicago's South Side.

Also Sunday, Senate Majority Leader Harry Reid, D-Nev., said the chances of Burris being sworn in are slim. Reid said he expected to meet with Senate Republican leader Mitch McConnell of Kentucky this evening in hopes "we can solve this issue on a bipartisan basis."

Opponents say Burris' appointment is tainted because it was made by Blagojevich, who is accused by federal authorities of offering to sell the vacancy to the highest bidder.

Burris, a former state attorney general, said the appointment is legal and the governor had the authority to do it. He has threatened to sue Senate Democrats if they refuse to swear him in as the chamber's only black member.

The second-ranking Democrat, Illinois Sen. Dick Durbin, acknowledged Blagojevich has the state constitutional authority to fill the vacancy.