Amtrak officials say they still expect to start carrying passengers by late August or early September on four high-speed train sets that have been undergoing tests on the New York-to-Washington stretch of the Northeast Corridor.

"I can't really split hairs around a couple of weeks," said Amtrak spokeswoman Lynn Bowersox. "Until they give us a date, I can't say what the delivery date would be."

The consortium building the train has to give railroad officials a "conditional acceptance date" to turn over the high-speed train equipment before Amtrak can determine when passengers can step on board the first Acela Express, she said.

Meanwhile, a spokesman for the consortium, Bombardier-Alstom, said the builders are keeping to a tight schedule to finish testing on the trains.

"We maintain our mid-summer commitment to delivery for conditional acceptance," said Gilles Page. "I can't be more precise."

Former Gov. Michael S. Dukakis, who serves as vice chairman of the Amtrak board of directors, said the testing problems that pushed back the Acela Express launch date appear to be resolved.

"At this point our hope is we can do this by the end of the summer," he said. "We're going to be pushing hard."

In comments last week at a conference of the National Corridors Initiative in Washington, Thompson, the Republican governor if Wisconsin who chairs the Amtrak board, said he was frustrated and angry that testing problems had extended the fast-train launch date into September.

He added that the railroad would enforce late-delivery penalties against the train consortium.

Amtrak had originally promised that the high-speed train would start carrying passengers from Washington to New York and Boston by the end of last year.

The project involved electrification of the track between New Haven and Boston, track improvements, and the introduction of new train equipment designed to tilt around curves at high speeds.

The electrification eliminated a time-consuming transfer from electric to diesel power at New Haven, paving the way for a three- hour train trip between New York and Boston that is expected to compete with existing air shuttles.

An Acela Regional train was introduced to the corridor in January, using some of the newly designed cars, but the introduction of the entire high-speed train set has been plagued by embarrassing delays.

Problems with the undercarriage design that triggered unexpected wheel wear were faulted for the first snafu, followed by limits on the tilting mechanism.

Then last month, Amtrak officials were forced to announce another delay after testing turned up broken and missing bolts on the wheel sets, known as "trucks."

Longer bolts appear to have solved the problem, officials said.

Jim RePass, president of the National Corridors Initiative, said testing of this kind rarely happens in such a public environment.

"In defense of Amtrak, I'd say if Boeing had to do its testing as Amtrak has had to do, stark naked here, nobody would fly," RePass said.