"My credentials were not in order, I will not be accepted, I will not be seated," Burris, 71, told a mob 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, who would be the Senate's only black member, also said he was considering a federal lawsuit to force Senate Democrats to seat him.

It was a major distraction for majority Democrats eager to project an image of progress with Obama on an economic stimulus package that could cost up to $1 trillion.

Democrats and Obama have said that the corruption charges against Blagojevich would strip credibility from anyone he appoints to the seat. Burris and many of his supporters have suggested that the real reason for the rejection involved race.

Blagojevich denies federal accusations that he tried to sell Obama's seat. Democrats, for their part, deny that race has anything to do with Burris' rejection and say that it's a reflection on Blagojevich.

That Secretary of the Senate Nancy Erickson turned away Burris was no surprise; Senate Democrats had warned for weeks 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.

But if what Burris really wanted a circus, he got one.

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. Once again Burris went through a metal detector and into Erickson's office, nestled between the elevators and the press gallery.

Twenty-one minutes later, Burris 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.

And soon, a noisy throng of reporters followed him across the street, and Burris confirmed that he'd been turned away.

An attorney for Burris, Timothy W. Wright III, said that "our credentials were rejected by the secretary of the Senate. We were not allowed to be placed in the record books. We were not allowed to proceed to the floor for purposes of taking oath. All of which we think was improperly done and is against the law of this land. We will consider our options and we will certainly let you know what our decisions will be soon thereafter."

Asked what his options were, Wright said there possibly could be a court challenge and he said that Burris also would continue to talk to the Senate leadership.

There had been earlier indications that the Senate would disallow Burris to take his seat, at least in part because his letter of appointment from Blagojevich was not co-signed by Illinois Secretary of State Jesse White.

Some of Burris' supporters have bemoaned the fact that Democrats would stand in the way of the Senate gaining its only black member. Burris himself downplayed the issue of race, telling reporters: "I cannot control my supporters. I have never in my life, in all my years of being elected to office, thought anything about race."

Earlier Tuesday, Burris had tense negotiations with Terrence Gainer, the Senate's sergeant at arms.

"I'm presenting myself as the legally appointed senator from the state of Illinois. It is my hope and prayer that they recognize that the appointment is legal," he said earlier in a nationally broadcast interview.

Burris dismissed the Senate Democratic leadership's position that he cannot be seated because he was appointed by a governor accused in a criminal complaint of trying to benefit financially from his authority to fill the seat that Obama vacated after winning the presidential election.

Burriss said his belief is that his appointment is constitutional and that "I have no knowledge of where a secretary of state has veto power over a governor carrying out his constitutional duties."

Burris also maintained that the announcement by Blagojevich Monday of a date for an election for a successor to Rep. Rahm Emanuel, D-Ill., proves the governor still has legal authority to carry out his duties. Emanuel will be Obama's White House chief of staff.

"There's nothing wrong with Roland Burris and there's nothing wrong with the appointment," Burris said.

Burris has found little support among fellow Democrats.

Senate Majority Leader Harry Reid, D-Nev., had said Monday that Burris would not be permitted to take his seat because Burris "has not been certified by the state of Illinois," a reference to incomplete paperwork that only touches on the dispute. Senate Democrats maintain that Burris' appointment is tainted because of the charges against Blagojevich.

While Blagojevich has signed formal appointment papers, White has not, and Senate rules require that signature. Burris, in turn, has gone to court hoping to win an order for White to sign the necessary paperwork, and he has also threatened to sue to take his seat in the Senate.