WASHINGTON – A conservative watchdog group has sued the Senate for refusing to immediately seat Roland Burris as the new senator from Illinois.

The lawsuit was filed Wednesday in federal court in Washington on behalf of an Illinois resident. The suit was filed by Judicial Watch, whose lawyers say the Senate's refusal to seat Burris is unconstitutional.

Burris was appointed by Illinois Gov. Rod Blagojevich (blah-GOY'-uh-vich) to the Senate seat vacated by President-elect Barack Obama.

Senate Democrats and Obama have said anyone appointed by Blagojevich, who is embroiled in a corruption investigation, would be tainted and should not be allowed to represent Illinois.

The Senate on Tuesday refused to swear Burris in with the rest of the new senators. But Burris said Wednesday he should be able to join the Senate soon.