The Senate is expected to vote Tuesday on whether to prohibit long-haul Mexican trucks from crossing into the United States, as part of the debate on a fiscal 2008 spending bill.

The amendment to the $104.6 billion Transportation-HUD measure (HR 3074) would bar funds from being used for a controversial Transportation Department pilot program allowing up to 100 Mexican trucking companies to operate in the United States beyond a 25-mile radius of the border.

The administration ordered the pilot program early this year, but Congress blocked it with a rider on the fiscal 2007 Iraq War supplemental bill (PL 110-28), pending a report by the Department of Transportation’s inspector general and a department response to that report.

The department issued that report Sept. 6 and triggered the program one hour later, said Sen. Byron L. Dorgan, D-N.D., who offered the amendment.

Dorgan said the department’s move ignored the inspector general’s finding that Mexican databases were insufficient to provide information about vehicle inspections, accident reports and driver records — “the entire guts of what you need to know if you’re going to ensure the safety of the American public,” Dorgan said.

The House adopted a similar amendment to its version of the Transportation-HUD measure before passing it July 24.

Republicans objected to a vote Monday on the Dorgan amendment, and it was not clear whether they would also seek to block action Tuesday.

The Senate adopted one amendment Monday that would free up $1 billion in added funding to upgrade aging bridges around the nation.

The amendment, by Patty Murray, D-Wash., would not directly appropriate the money. Rather, it would allow an extra $1 billion to be obligated directly from the Highway Trust Fund.

The funds would be distributed as grants to states based on a formula enacted in the 2005 highway law (PL 109-59).

The amendment, a response to the Aug. 1 collapse of an interstate highway bridge in Minneapolis that killed at least 13 people, was adopted, 60-33.

Many Republicans, led by Christopher S. Bond, R-Mo., objected to the amendment on grounds that it would exacerbate predicted shortfalls in the Highway Trust Fund, which is fueled by the federal gasoline tax rather than annual appropriations.

The Office of Management and Budget says the trust fund could have a shortfall of $3.8 billion to $4.3 billion by fiscal 2009 unless lawmakers find new revenue streams or significantly cut highway spending.

“We should not overreact to the Minnesota bridge collapse by spending more money out of the Highway Trust Fund than is available,” Bond said, adding that the issue should be handled as part of the next surface transportation reauthorization. The current law expires in 2009.

Murray said the amendment was not a “budget buster” and contained a stipulation to prohibit states from shifting the money for bridge repairs to other priorities, as states can do with other grants from the trust fund.

Senators are working against the clock to finish the bill by 1 p.m. Wednesday, which Majority Leader Harry Reid, D-Nev., has set as the deadline for roll call votes before the Senate recess for Rosh Hashana.