Former major leaguer Jose Canseco told Congress in a sworn affidavit that he has never seen Roger Clemens "use, possess or ask for steroids or human growth hormone."
The Associated Press obtained the affidavit, dated Jan. 22, on Tuesday.
It is part of the evidence gathered by the congressional committee looking at drugs in baseball.
The House Committee on Oversight and Government's hearing Wednesday will focus on Clemens' denials of his former personal trainer's allegations in the Mitchell Report.
The trainer, Brian McNamee, told federal prosecutors and then-baseball investigator George Mitchell that he injected Clemens with steroids and human growth hormone at least 16 times in 1998, 2000 and 2001.
"I have never had a conversation with Clemens in which he expressed any interest in using steroids or human growth hormone," Canseco said in the affidavit. "Clemens has never asked me to give him steroids or human growth hormone and I have never seen Clemens use, possess or ask for steroids or human growth hormone."
Canseco continued: "I have played on three teams with Roger Clemens and I have no reason to believe that he has ever used steroids, human growth hormone, or any other performance-enhancing drugs."
According to McNamee, Clemens first raised the subject of steroids not long after McNamee saw Canseco and Clemens at a June 1998 party.
At the time, Canseco and Clemens were teammates on the Toronto Blue Jays, and McNamee was working for the team.
Canseco says in his affidavit Clemens was not at that party.
The first mention of Clemens' name in the Mitchell Report is on page 167.
On the very next page comes McNamee's account of "a lunch party that Canseco hosted at his home in Miami."
The report says, "McNamee stated that, during this luncheon, he observed Clemens, Canseco, and another person he did not know meeting inside Canseco's house, although McNamee did not personally attend that meeting."
In his affidavit, Canseco said, "I specifically recall that Clemens did not come to the barbecue. I remember this because I was disappointed that he did not attend. I later learned that he had a golfing commitment that day and could not attend the party."
Canseco penned 'Juiced'
Canseco's book about steroids in baseball, Juiced, drew Congress' attention in 2005, leading to a hearing with Mark McGwire, Sammy Sosa and Rafael Palmeiro.
In addition to the 1998 Blue Jays, Canseco and Clemens were teammates on the 1996 Boston Red Sox and 2000 New York Yankees.
In his affidavit, the existence of which was first reported by the AP on Saturday, Canseco also disputes other McNamee statements contained in the Mitchell Report.
The affidavit says, "neither Senator Mitchell nor anyone working with him" contacted Canseco to attempt to corroborate what McNamee said.
Two of McNamee's lawyers did not immediately return calls for comment Tuesday.
But on Saturday, McNamee lawyer Earl Ward said he did not think Canseco's affidavit would be meaningful.
Reached Tuesday by the AP, Canseco said, "I've been told not to say anything."
His lawyer said Canseco would not attend Wednesday's hearing.
Clemens and McNamee are the two main witnesses.
Three others originally invited to testify were excused Monday, including Yankees pitcher Andy Pettitte, who is a former teammate and workout partner of Clemens.
McNamee also told Mitchell that Pettitte used HGH.
Two days after the Mitchell Report was released, Pettitte acknowledged he did try HGH.