Also during today's floor debate, the Senate approved an amendment sponsored by Barbara Mikulski (D-MD) that allows individuals to claim an above-the-line tax deduction on loan interest -- and related state sales and excise taxes -- associated with purchasing certain automobiles.

A proposal by Sen. Patty Murray (D-WA) that failed on a procedural vote would have directed an additional $25 billion towards highway, mass transit and water infrastructure investments.

The underlying Senate stimulus bill provides $27 billion for highway investments, $3.1 billion for rail transportation projects, and $5.5 billion for competitive grants to state and local governments for transportation investments. The Murray amendment, if adopted, would have boosted highway spending by $13 billion and distributed the additional funding via formula grants to states and local governments.

"This amendment invests in tried and true projects that get laid-off workers back on the job and pave the way for future economic strength," Murray said. "These are the investments mayors and governors across the country are asking for and this amendment answers the call."

Murray is the chairman of the Senate Appropriations Subcommittee on Transportation and Housing.

A final vote on the bill is expected by week's end, although a weekend session is possible. The House passed its version of the stimulus bill last week. House and Senate negotiators will have to hammer out a final version once the Senate completes work on its version.