Updated

Mark McGwire (search) plans to comply with a subpoena and attend Thursday's congressional hearing into steroid use in baseball, The Associated Press has learned.

McGwire's decision, revealed Wednesday by a representative of the former Oakland and St. Louis slugger who spoke on condition of anonymity, made it likely all six subpoenaed players would attend the session on Capitol Hill (search).

Less than 24 hours before the start of the highly anticipated hearing, Jose Canseco's (search) request for immunity was denied by the House Government Reform committee, which also revealed that baseball's drug-testing agreement contains a provision that testing would be "suspended immediately" if the government conducts an independent investigation into drug use in baseball.

"I can reach no conclusion but that the league and the players' union have misrepresented to me and to the American public the substance of MLB's new steroid policy," he said. "I expect the league and the players' union to modify the new policy to comply with at least what was announced by MLB in January. To do anything less than that would constitute a violation of the public's trust, a blow to the integrity of Major League Baseball, and an invitation to further scrutiny of the league's steroid policy."

Canseco's lawyer said the former AL MVP will not be able to answer questions that would incriminate him.

"No witnesses have been or will be granted immunity," David Marin, a spokesman for committee chairman Rep. Tom Davis, said in an e-mail to the AP.

Canseco's lawyer, Robert Saunooke, was angry with the decision.

"It begs the question as to what they're convening this hearing for," Saunooke said in a telephone interview. "They effectively cut the legs off from underneath us."

Saunooke has said that without immunity, Canseco would invoke his Fifth Amendment right to refuse to answer questions.

"They told me we can't do the Fifth to every question," he said. "It's an absolute right of every citizen to not be compelled to give testimony against themselves. They do not make the decision. We do."

As an example of how immunity would limit Canseco, Saunooke brought up McGwire's repeated denials of steroid use.

"If he still holds to that lie, then the only way we can disprove that is to give specific instances and talk openly and freely," Saunooke said. "If we can't do that, then our credibility is undermined."

Boston pitcher Curt Schilling said he will comply with the subpoena, and Chicago White Sox trainer Herm Schneider said that Frank Thomas left Tucson, Ariz., on Tuesday, would stop at his home in Las Vegas, then would travel to Washington. Sammy Sosa and Rafael Palmeiro also were headed to Washington, Baltimore Orioles vice president Mike Flanagan said.

New York Yankees slugger Jason Giambi, who also was subpoenaed last week, was excused Tuesday from testifying because of his involvement in the ongoing federal investigation into illegal steroid distribution.

"I would have done whatever they would have asked me to do and go from there," Giambi said Wednesday at the Yankees' training camp in Tampa, Fla. "They gave me an opportunity to focus on baseball so I appreciate that."

Baseball commissioner Bud Selig, union head Donald Fehr, baseball executive vice presidents Rob Manfred and Sandy Alderson and San Diego general manager Kevin Towers also will testify.

President Bush, the former Texas Rangers owner, refused to say whether the decision to subpoena players was an abuse of congressional power.

"I'm wise enough not to second-guess the intentions of the United States Congress," he said. "I do appreciate the public concern about the use of steroids in sport, whether it be baseball or anywhere else, because I understand that when a professional athlete uses steroids, it sends terrible signals to youngsters."

Canseco, whose recent book accused several baseball stars of using steroids, submitted an opening statement to the committee in which he said "I did not know that my revelations would reverberate in the halls of this chamber and in the hearts of so many." Canseco's statement was first reported on the Web site of The (Baltimore) Sun, then obtained by the AP.

"I had hoped that what I experienced firsthand, when revealed, would give insight into a darker side of a game that I loved," he said, "that maybe it would force baseball to acknowledge it condoned this activity for the sole purpose of increasing revenue at the gate. Unfortunately, by our presence here today, it is clear that MLB is not interested in admitting the truth."

Canseco said he had endured criticism because of Major League Baseball.

"All of these attacks have been spurred on by an organization that holds itself above the law, an organization that chose to exploit its players for the increased revenue that lines its pockets and then sacrifice those same players to protect the web of secrecy that was hidden for so many years."

Davis and Rep. Henry Waxman, the ranking Democrat, sent a letter to Selig and Fehr on Wednesday questioning why baseball's drug-testing agreement gives the commissioner discretion to fine a first-time offender $10,000 instead of imposing a 10-day suspension. They also expressed concern that only the suspension would be announced, not which substance a player tested positive for, and pointed out that Olympic athletes receive longer suspensions for positive tests.

The congressman also said four steroids that are prohibited by the World Anti-Doping Agency — boldione, danazol, quinbolone and dihydroepiandrostone — are not banned by baseball and asked why baseball did not ban amphetamines.