WASHINGTON -- Health and Human Services Secretary Tommy G. Thompson, one of Amtrak's biggest supporters, announced Friday that he would step down as chairman of the national passenger railroad's board, reports the Milwaukee Journal Sentinel.

Rail backers mourned Thompson's departure and said they weren't sure who would take over leadership of efforts to establish high-speed rail nationwide - including a planned Midwestern network that would start by running 110-mph trains from Milwaukee to Madison in late 2003.

As Amtrak chairman, the former Wisconsin governor has been an energetic and vocal advocate for high-speed rail. He touted the fast trains both as Amtrak's financial savior and as the solution for travelers weary of crowded highways and airports.

Thompson had fought hard to keep the Amtrak post after being named to President Bush's cabinet, despite reports he wouldn't be allowed to hold both jobs. At one point, he indicated that the embattled railroad's congressional foes wanted him out of the way.

But in the end, Thompson acknowledged that federal law allows only one cabinet member to sit on the board - and as long as Thompson was on, Transportation Secretary Norman Mineta couldn't take the seat that was meant for him.

"As you know, I am passionate about Amtrak and the great potential for high-speed rail to improve the quality of transportation and life in this nation," Thompson wrote in a letter to Bush. "But I also understand and appreciate . . . the need for the secretary of transportation to be represented on the board."

Mineta had told a rail conference Thursday that he expected to replace Thompson on the board, and Thompson wrote that he was "completely confident" that Mineta "will do a tremendous job on the Amtrak board." A White House spokesman did not return a call seeking comment on whether Bush would appoint Mineta to the board.

In a separate written statement, Thompson said he would step down after the board's May 23 meeting. Then-President Bill Clinton named Thompson to a term expiring in 2003.

If Bush names Mineta to the board, the Democratic appointee of a Republican president would replace the Republican appointee of a Democratic president. It also would mark the second time in less than six months that Mineta won a job coveted by Thompson, who had sought to become transportation secretary.

Through a spokesman, Mineta said, "Secretary Thompson has done a great job. Everyone in the industry recognizes his contributions to America's passenger rail system. I look forward to working on the challenges that remain."

Not everyone was so kind. Amtrak critic Joe Vranich, who has been calling for Thompson's ouster for nearly a year, said his departure was overdue. Vranich, a California writer and early Amtrak supporter, accused Thompson of misleading Congress and the public about the extent of the railroad's financial troubles.

Neither Thompson nor his spokesmen could be reached for further comment. But in the past, Thompson has dismissed Vranich's claims and has insisted that Amtrak is on track to meet its congressional deadline to become financially self-sufficient by Oct. 1, 2002.

And in his own written statement, Amtrak President George Warrington said, "Secretary Thompson's leadership was crucial to the record-breaking ridership and revenue gains that Amtrak posted during his tenure."

Thompson's contributions to Amtrak also won praise from Wisconsin Transportation Secretary Terry Mulcahy, Patricia Robbins, vice president of the Wisconsin Association of Rail Passengers, and Scott Leonard, assistant director of the National Association of Rail Passengers.

Although it's not clear who will become the chief advocate for high-speed rail, Leonard said, "Tommy Thompson will remain one of our best supporters, no matter where he is."