Federal authorities did not deem the claim credible.

An upcoming book about Rod Blagojevich says undercover recordings caught the former governor saying he had heard that convicted influence peddler Antoin "Tony" Rezko secretly channeled $25,000 in cash to Barack Obama, but federal authorities did not deem the claim credible.

The book, "Golden: How Rod Blagojevich Talked Himself Out of the Governor's Office and Into Prison," suggests Blagojevich was talking about an undisclosed payment to help Obama with his 2004 campaign for the U.S. Senate.

The book says that federal investigators pursued the claim but ultimately gave it little credence. "Never was Blagojevich seen as a credible threat to the incoming president," says the book, an outside project by two Chicago Tribune reporters.

The White House referred questions about the matter to the Obama campaign. Ben LaBolt, a campaign spokesman, said the claim "is preposterous and it is false. No such payment was ever offered or made, and there never has been any suggestion or question of it from anyone, except apparently by Rod Blagojevich."

Federal authorities declined to comment to the Tribune about the investigation.

An attorney for the now-imprisoned Rezko dismissed the allegation, saying Blagojevich's claim is "simply a fabrication and not true."

"You must keep in mind that the source of this allegation is inherently unreliable and not credible," said the attorney, Joseph J. Duffy.

Blagojevich's lawyer, Sheldon Sorosky, did not return calls. Another of his attorneys, Lauren Kaeseberg, declined comment.

The disclosure of Blagojevich's comments comes as the president is locked in a tight re-election campaign with Republican Mitt Romney, the former Massachusetts governor, who has sought to link Obama's Chicago connections to the city's culture of political corruption.

Obama's ties to Rezko were a nagging issue in the 2008 campaign. Rezko and Obama were friends, and Rezko raised as much as $250,000 for Obama for the first three political offices he sought. Obama also acknowledged a lapse in judgment over his involvement with Rezko in private real estate transactions related to the purchase of Obama's home in the Kenwood neighborhood in 2005.

Blagojevich's claim about the money was caught on a government recording that was not made public during either of Blagojevich's trials, according to the book. The book, by Jeff Coen and John Chase, does not say who gave the recordings to the authors.

The accusation of money paid indirectly to Obama is among many musings by Blagojevich that the FBI secretly recorded. Among the others: that Blagojevich mentioned naming Oscar-winning actress Halle Berry to Obama's vacant Senate seat so he could "have a shot" at having sex with her. Blagojevich, a Democrat, also told a staffer he voted for RepublicanGeorge H.W. Bush for president and then gave the staffer a warning: "If you ever repeat this, first I'll deny it, secondly I'll wait a little bit, then I'll fire you."

The book portrays Blagojevich as being envious that Obama's political fortunes had risen so high when the governor thought the incoming president had bigger Rezko problems than he did.

According to the book, Blagojevich was repeating "a story that (he) had heard that he believed" when he spoke of the $25,000 in cash from Rezko. Talking to his then-chief of staff John Harris shortly after Obama's election, Blagojevich said he had heard that Rezko had given the cash to Bruce Washington, who has held jobs with the state, Cook County and the city school district.

"The cash was for Obama. Not for me," Blagojevich told Harris, according to the book.

"Right," Harris replied.

"You understand?" the governor asked.

At one point, in a conversation with his wife, Patti, Blagojevich even tossed out the idea of naming Washington to Obama's Senate seat.

"How about I make him the [expletive] senator?" Blagojevich asked his wife, according to the book.

The Tribune began seeking comment from Washington, 60, late last week after learning of Blagojevich's claims. He did not respond to letters the Tribune left at his home or to phone messages.