Mr Burris is being investigated by the Senate Ethics Committee
Illinois Senator Roland Burris has denied that he attempted to "buy his seat" from the state's disgraced former Governor Rod Blagojevich.
The denial comes a day after a judge released a transcript of a wiretapped conversation between Mr Burris and Mr Blagojevich's brother.
Mr Burris offered to "personally do something" for Mr Blagojevich's campaign fund, the transcript revealed.
Mr Blagojevich was charged last year with trying to "sell" the seat.
As governor, it was Mr Blagojevich's responsibility under state law to pick someone to replace Barack Obama when he became US president.
He was arrested on 9 December and charged with corruption.
After his arrest, officials published transcripts of Mr Blagojevich's wiretapped conversations, in which the ex-governor was overheard discussing what he could get in return for the seat.
He eventually picked Mr Burris to fill the vacancy.
At the time of his appointment, Mr Burris denied that he had spoken to any members of the governor's team about the senate seat, but later acknowledged that he had discussed it with Blagojevich aides.
The newly-released transcript indicates that Mr Burris spoke about the seat to Mr Blagojevich's brother Robert, who was in charge of fundraising for the former governor.
"I mean, so Rob, I'm in a dilemma right now wanting to help the governor," Mr Burris told Robert Blagojevich, according to the transcript.
"I know I could give him a check," Mr Burris added. "Myself... I will personally do something, okay."
"God knows No. 1, I wanna help Rod," he continued. "No. 2, I also wanna, you know, hope I get a consideration to get that appointment."
But the transcript reveals that Mr Burris was aware of the impression that a donation to Mr Blagojevich might give.
"If I put on a fundraiser now... it has so many negative connotations that Burris is trying to buy an appointment from the governor for the senate seat."
Mr Burris has rejected the claim that the transcript indicates he was trying to offer the governor cash in return for the senate seat.
"Did I try to buy the seat? Never," Mr Burris told reporters on Wednesday.
"If you look at the transcript you can see what I was saying I did not know anything about a pay-to-play. I knew if I raised money, it would be a problem."
The Senate Ethics Committee is investigating Mr Burris's appointment and will take the transcript into account when making its report.
Mr Blagojevich was removed from his position as Illinois governor on 29 January.
He was indicted by a federal grand jury last month on corruption charges and is currently awaiting trial.