Blagojevich asked the media not to visit any of his political troubles on Burris as he made the announcement at a news conference in Chicago, Illinois.

FBI agents arrested Blagojevich on December 9 after federal prosecutors alleged, among other things, that he had tried to "sell" Obama's former Senate seat.

The governor denies any wrongdoing and has ignored calls to resign.

Obama's office declined to comment on the appointment.

A spokesman for US Attorney Patrick Fitzgerald, who is pursuing Blagojevich's corruption charges, refused to comment on the issue.

Burris, 71, served Illinois from 1979 to 1992 -- first as state comptroller and later as attorney general.

Earlier this month, he said that despite the scandal associated with the seat, he wanted the job.

Burris does not have to be formally approved by the Senate to be appointed by Blagojevich, but the Senate could refuse to seat Burris, or it could seat him and investigate the manner in which he was appointed, and unseat him if senators discover any wrongdoing.

Two Democratic officials said Senate Democratic leaders are planning to block Blagojevich's appointment of Burris.

Senate Majority Leader Harry Reid, a Democrat of Nevada, has threatened not to seat anyone the governor appoints and has called for Blagojevich, a Democrat, to step down.

Although Blagojevich, 52, has not commented publicly on the charges, his lawyer Ed Genson said the governor has done nothing wrong and does not intend to step down.

It is the sole authority of the Illinois governor to name a successor to serve the remaining two years of Obama's term.