Amtrak next month will resume Acela high-speed train service, which was suspended in April because of brake problems, the railroad's chief of operations said yesterday.

The return will be gradual, with all 20 Acela trains back in service in the fall after repairs are made, William L. Crosbie said at a House Transportation Committee hearing in Washington. He didn't give a specific month.

The trains, which can reach 150 miles an hour, serve New York, Washington and Boston, and account for more than 20 percent of Amtrak's ticket sales. Amtrak has said the suspension of Acela service has cost it about $1 million a week.

The trains, made by Bombardier Inc. and Alstom SA, were taken out of service April 15 after inspectors found cracks in about 20 percent of brake rotors.

The railroad is testing a new type of rotor to replace the cracked ones, Crosbie said. The replacements change the rotor design to reduce vibrations when the brakes are applied, said R. Clifford Black, an Amtrak spokesman. The vibrations may have caused the cracks, Black said.

Amtrak has been working with equipment suppliers such as Knorr Brake, a unit of closely held Knorr-Bremse AG of Munich, to develop the replacement parts.

Metroliner trains, which take about 15 minutes longer than Acelas to reach New York from Washington, have run the 15 weekday New York-Washington round trips since April.

The Acela problems arose as Congress debated funding for Amtrak, which has received about $30 billion in subsidies since it was founded in 1971, including $1.2 billion this fiscal year.

The railroad originally expected to have $75 million when the fiscal year ends on Sept. 30 and now forecasts the amount will be as little as $35 million.

Acela has been an "incredible fiasco," Rep. John L. Mica (R-Fla.) said at the hearing. The high-speed trains were delayed almost a year by flaws such as wheel cracks before starting in 2000. The trains also were suspended in 2002 after shock-absorber parts cracked.

Mica also criticized Amtrak for losses on food service, in part because of high labor costs.

Fred E. Weiderhold Jr., the railroad's inspector general, said yesterday that Amtrak loses more than $130 million a year on food service. The railroad could reduce costs by $94 million by paying its food-service workers wages similar to those of restaurant employees and by reducing expenses for food storage, he said.

Amtrak workers receive 3.5 times the average annual compensation of about $15,000 for restaurant employees, Weiderhold said.