WASHINGTON, DC - The $8 billion in stimulus cash awarded to 13 high-speed rail corridors across the country may seem like a windfall for advocates, but there's a catch: The money isn't enough to finish any of the major projects.

State coffers are dry and federal spending is being cut back, so it's unclear who, if anyone, will pay the rest of the multi-billion dollar bill.

Many states have been vague about how they would foot their part of the bill. But experts say most are counting on the federal government to cover at least half of their costs over the next few decades a hope that may clash with President Barack Obama's recent pledge to curb spending.

"As time goes on, as fast trains become a way of life for America, there will be more and more federal help," Ill. Gov. Pat Quinn said Friday after his state learned it would get more than a $1 billion of the stimulus money.

Optimists point to the 2011 federal budget Obama proposed Monday that seeks $1 billion more for high-speed trains on top of the $8 billion he announced in stimulus money last week. There's another $2.5 billion tucked away in the 2010 federal appropriations bill that has been approved but not yet allocated.

A proposed $500 billion, six-year federal transportation reauthorization bill includes $50 billion for high-speed rail. But that generous sum was included before Obama began talking about belt tightening, and it seems unlikely to win approval in its current form.