NEW YORK - While Jason Giambi was excused, Frank Thomas and Curt Schilling made plans to appear at a congressional hearing on steroids in baseball.

Baltimore's Sammy Sosa and Rafael Palmeiro were given the day off Thursday, an indication they also may testify.

Jose Canseco already has said he'll be there, but it's unclear whether Mark McGwire will show up and comply with the subpoena he was issued last week.

Giambi does not have to go to Washington because of his involvement in the ongoing federal investigation into illegal steroid distribution, House Government Reform committee chairman Rep. Tom Davis and ranking Democrat Rep. Henry Waxman said Tuesday. Giambi testified in 2003 before a grand jury probing the Bay Area Laboratory Co-Operative, and the San Francisco Chronicle reported in December that he admitted before that panel that he had used steroids.

"I appeared in front of the federal grand jury a year ago. I answered every question, told the truth and cooperated fully," Giambi said in a statement released by his agent. "I appreciate that the members of the committee evaluated my situation, and I will now continue to focus on playing the best baseball I possibly can."

BALCO founder Victor Conte, BALCO vice president James Valente, Barry Bonds' trainer Greg Anderson, and track coach Remi Korchemny were indicted in the case, and trial dates have not yet been scheduled. A hearing was postponed Tuesday, with Anderson's lawyer saying her client would prefer a deal.

Bonds and Gary Sheffield, who also testified before the grand jury, weren't among the seven current and former players subpoenaed by the committee last week.

In a letter sent to the committee accompanying more than 400 pages of documents Monday, baseball executive vice president Rob Manfred said just 12 of 1,133 tests last year were positive, and that positive tests from nandrolone dropped from 73 in 2003 to one last year.

Davis and Waxman waited until Tuesday night to make the announcement on Giambi.

"From the outset, we have said that we in no way wanted our inquiry to impede or complicate any ongoing investigations by law enforcement," they said in a joint statement. "Upon hearing today from the Justice Department that Mr. Giambi's appearance could do just that, we have decided to excuse him from testifying. All other invited witnesses, however, will be expected to comply with the subpoenas issued to them last week."

In a telephone interview with The Associated Press, Waxman left open the possibility that other witnesses could be excused.

"It's still a dynamic process," Waxman said. "We're still talking to the different subpoenaed witnesses. Until you hear otherwise, we expect them there. I expect everybody to be there. And the only reason Giambi is being excused is the Justice Department's request that he not testify because it might interfere with other ongoing investigations they're doing."

Luke Macaulay, spokesman for the U.S. Attorney in San Francisco, wouldn't comment on the decision to excuse Giambi.

Waxman said he and Davis wouldn't try to get players to implicate others.

"Chairman Davis and I are not going to ask anybody to name any names of people who have used steroids. I don't think that would be proper in a public forum," Waxman said. "With that exception, there are no limits on the questions that we've agreed to. It may be part of the further discussions that have not yet been resolved."

The committee accepted baseball commissioner Bud Selig's offer to testify. Baseball executive vice presidents Manfred and Sandy Alderson also will testify, as will San Diego Padres general manager Kevin Towers and union head Donald Fehr.

Chicago White Sox trainer Herm Schneider said Thomas left Tucson, Ariz., on Tuesday, would stop at his home in Las Vegas, then would travel to Washington. Marc Altieri, McGwire's spokesman, couldn't say whether his client will appear.

Canseco met with Davis on Monday. The committee hasn't yet responded to Canseco's request for immunity, which would allow him to speak more freely.

"The committee will release the information as to the conditions for witnesses all at once, rather than one at a time," Waxman said.

Manfred's letter Monday said "there were unresolved disputes" with 13 of the 96 positive tests in 2003. He said that if all the positives were accurate, there were 73 for nandrolone, 26 for stanozolol, eight for elevated testosterone, five for boldenone, three for methandrostenolone and one for clenbuterol. Some tests include positives for more than one substance.

Manfred said baseball didn't have results from "for cause" tests given to players since 1990 because they went directly to doctors. He said those results also are protected by doctor-patient privilege.

Contents of Manfred's letter were first posted on the Web site of The New York Times, and a copy of the letter later was obtained by the AP.