At least one Rust Belt lawmaker will not back an extension of the bankrupt "Cash for Clunkers" program in light of Congress' efforts to fast track an extension and additional funding for the auto voucher service.

Sen. Claire McCaskillClaire Conner McCaskillNSA spying program overcomes key Senate hurdle Senate campaign fundraising reports roll in Dems search for winning playbook MORE (D-Mo.), who is a centrist Democrat, tweeted her opposition to the program's renewal on Thursday:
I will vote no on any extension of Cash for Clunkers program.

The junior senator did not state any reasons for her decision as of this post.

The House this morning introduced stand alone legislation that would allocate $2 billion from the stimulus package toward funding an extending "Cash for Clunkers."

After only six days of operation, the program burned through $1 billion of vouchers given to potential car buyers who seek to trade in their low mileage vehicles for more fuel efficient ones.

UPDATED [1:53pm]: McCaskill offered an explanation for her stance, tweeting Friday:
We simply cannot afford any more taxpayr $ to extend cash for clunkers. Idea was to prime the pump, not subsidize auto purchases forever.

We put a billion $$ in cash for clunker program.That's 250,000 cars. We weren't sure how long it would last,but a billion of your $ is alot.

Cross-posted to the Twitter Room