Accepting the federal money would mean that Sound Transit must complete a 7-mile "central link" from South Lander Street in Seattle to 45th Street in the University District -- the portion that the grant addresses.

That would send the agency headlong into a project still fraught with financial and legal uncertainties. So why the rush?

President Clinton's transit administrators, the people with whom the agency has worked for more than a year to secure the $500 million, multiyear grant, give up their positions in two weeks and won't be replaced until the Senate confirms President-elect George W. Bush's appointees. The agency must act to avoid delaying or even losing its shot at the money, White and Earling said.

Sound Transit's application for the federal money last year was recommended by the Federal Transit Administration and survived a 60-day congressional review based on a cost-benefit analysis and the region's ability to pay nearly 70 percent of the system's costs. The 22-mile rail system is financed largely by a 0.4 percent sales tax and a 0.3 percent motor vehicle excise tax approved by voters in 1996.

But the FTA held back on issuing the grant for reasons it refused to disclose.

Then Sound Transit suspended negotiations with Modern Transit Constructors, the firm selected to design and build the 4.5-mile rail tunnel from downtown Seattle to the University District, because its construction cost estimates were much higher than Sound Transit's.

As a result, the agency's light-rail director resigned. And new leaders came up with a revised price of $3.6 billion and a delay until 2009.

Now, Sound Transit officials say the FTA has adjusted its proposed grant agreement to reflect the cost and schedule changes and promised to award the grant -- on the condition the agency commits to continuing.

Earling said this is the third time in 30 years that the Seattle area has had a chance at getting federal money for light rail and this time they will snatch it up.

"The board is of the mind that we can't wait another generation," he said. "We're going to have to move forward on this, or we will have an insurmountable obstacle."

Critic John Niles said plunging into a federal grant agreement is irresponsible.

"A change in the cost by itself (with no additional riders) means the whole project should be carefully re-examined by both the public and the FTA."

Bruce Frame, FTA spokesman, has said that it's not unusual for costs to change as transit projects progress, nor do higher costs ruin the agency's chances of securing the grant. Sound Transit officials say ridership estimates are good enough to justify the higher cost of the line.

Tuck Wilson, the agency's interim light-rail director, said once the grant agreement is signed the agency can still improve the project and reduce the cost on final design. He said extending the rail tunnel to Ravenna is such an opportunity.

Instead of ending on 45th Street, it would continue to either Northeast 58th Street or Northeast 75th Street. At those locations, tunnel builders could remove dirt at street level rather than out the long vertical shaft that stopping at 45th Street would require.

"It's safer, quicker and helps with schedule and cost," Wilson said, adding that the northern extension would also help move the line closer to Northgate -- a goal shared by many board members.

The Sound Transit board will choose between a tunnel exiting on Eighth Avenue at Northeast 58th Street near Interstate 5 or near Northeast 75th Street on 12th Avenue, the option preferred by neighborhood residents, during the next six months.

Penny Eckert, president of the Roosevelt Neighborhood Association, said the Eighth Avenue alignment has always been unacceptable to the neighborhood.

Although the construction project would involve some inconveniences, exiting in Ravenna "makes sense to me. That would provide a huge incentive to continue north. As quaint at this neighborhood is, it wouldn't make any sense to make this the northern terminus of the line."

Wilson added that the agency will seek $900 million for light rail in the next federal funding cycle.

Wilson admits that the plan assumes collecting taxes for a longer period than originally envisioned -- which has prompted calls for another election.

He said completing the project within the more realistic cost and schedule estimates will restore public trust.

And agency officials say another public vote is out of the question.

King County Executive Ron Sims, a Sound Transit board member, said voters have already spoken and other options are too costly or impractical.

"Rail is the alternative. And the voters knew that when they voted for it," he said.