WASHINGTON — Roland Burris tried to take President-elect Barack Obama's Illinois Senate seat Tuesday but failed in a scripted piece of political theater staged just before the opening of the 111th Congress.

"Mr. Burris is not in possession of the necessary credentials from the state of Illinois," declared Senate Majority Leader Harry Reid of Nevada.

Burris, 71, earlier confirmed that Secretary of the Senate Nancy Erickson had informed him in a private meeting that his credentials lacked a required signature and his state's seal.

He said he had been advised that "I would not be accepted, and I will not be seated, and I will not be permitted on the floor." He spoke to a crowd of reporters who had followed him across the street for a news conference in a cold and steady rain outside the Capitol.

The former Illinois attorney general said he was "not seeking to have any type of confrontation" over taking the seat that he was appointed to by embattled Gov. Rod Blagojevich. But Burris also said he was considering a federal lawsuit to force Senate Democrats to seat him.

It was a distraction for majority Democrats eager to project an image of progress with Obama on an economic stimulus package estimated to cost as much as $800 billion.

Democrats and Obama have said that the corruption charges against Blagojevich would strip credibility from anyone he appointed to the seat.

Blagojevich denies federal accusations that he tried to sell Obama's seat.

In a written statement following Tuesday's action, the governor said allegations against him shouldn't be held against Burris, whom he called a "good and decent man."

"The people of Illinois are entitled to be represented by two senators in the United States Senate," Blagojevich said.

That Erickson turned away Burris was no surprise; Senate Democrats had warned that if Burris showed up to be sworn in on Tuesday without the signature of the Illinois secretary of state, he would be turned away. That's just what happened.

A mob of reporters awaited him outside the Senate's North Door, where Sergeant at Arms Terrance Gainer and a throng of officers escorted him through security and up to Erickson's office on the third floor.

There, more reporters waited. Burris went through another metal detector and into Erickson's office, nestled between the elevators and the press gallery.

Twenty-one minutes later, he left. A spokesman for Senate Majority Leader Harry Reid confirmed that Burris had been rejected.

Burris left the building, escorted by Gainer and his officers.