Advocates for the Triangle Transit Authority's proposed commuter trains were not ready Thursday to quit their decade-long fight for federal funding, but their confidence was shaken as they weighed the increased odds stacked against their success.

U.S. Sens. Elizabeth Dole and Richard Burr warned in a letter Wednesday that the project probably would fall far short of federal requirements.

They recommended that TTA explore other options.

"It's a sobering letter," said Ellen Reckhow, chairwoman of the Durham County commissioners and a TTA trustee. "I hope that the jury is out. But this is a big setback for us, and I'm not taking it lightly."

Dole no longer looked like the political champion TTA would need to win a crucial waiver of a strict new cost-effectiveness standard applied to the rail project this year. In November, she had criticized the new rule as unfair.

But in their letter Wednesday, she and Burr said the TTA project appeared unlikely to qualify even under the less stringent standard that had governed its design over the past decade.

John Claflin, TTA general manager, said the Dole-Burr letter left him wondering how the project could find the backing it would need in Washington.

He said the Federal Transit Administration this week gave TTA until Sept. 30, 2006, to answer a number of lingering questions about the project and to provide new estimates of train ridership and cost-effectiveness.

"It's our intent to provide cost-effectiveness that meets the old guidelines, and then we'll have to see if we can talk Dole into supporting the waiver to use the old guidelines, like she had said she would," Claflin said.

Dole's office declined to comment. "The letter speaks for itself," spokeswoman Lindsay Mabry said.

FTA officials did not return calls seeking comment.

Burr's spokesman, Doug Heye, said some TTA supporters had overreacted to the letter. He said it was a snapshot of the rail project status as outlined this week by FTA officials.

A misinterpretation?

"Nothing in the letter opposes TTA," Heye said. "Nowhere does it say 'never.' It says the rail project is 'likely not an option.' It does not say it is not an option."

U.S. Rep. David Price, a Chapel Hill Democrat, said the Republican senators had misinterpreted the federal agency's evaluation.

Price and Claflin said the FTA applied an overall "low" rating to the TTA project as a temporary label until it receives all the information it needs to make a complete evaluation.

"Now it was also said that TTA has considerable work to do there, and there are some important unresolved issues," Price said.

He said he would help TTA pursue the rail project rather than explore alternatives as suggested by Dole and Burr.

'A plan for success'

"We're focused right now on developing a plan for success," Price said. "If other options need to be considered down the road, we'll do that when the time comes."

Crucial analysis

The News & Observer reported in a series of reports in October that TTA rail project costs had soared in the past 10 years from $100 million to $810 million, and that its local funding sources were weak.

An analysis of ridership forecasts showed that the Triangle would be the least-dense region in the nation to build a commuter train system.

Some local observers rebuked Dole in November for supporting a transit project they criticized as wasteful.

Nick Tennyson, a Republican former Durham mayor, said he hoped TTA would find the backing it needed in Washington. Charlotte's transit project had political clout, he said, because local residents approved a sales tax increase to help pay for it.

"Absent some tangible popular support like that, I don't see any politician on the planet who's going to go too far out on the limb for this," Tennyson said.