WASHINGTON -- The Senate came under increasing pressure Monday to refuel the stalling "cash-for-clunkers" initiative amid uncertainty over how much money, if any, is left in the fund bankrolling the popular program, according to The Associated Press.

The Obama administration pushed for an additional $2 billion after serving notice over the weekend that the program could expire as early as this week unless the Senate acts, as the House did in voting overwhelmingly for the money last Friday.