Congress has five days to prevent a highway-funding shutdown, with federal transportation spending currently set to expire on Dec. 4.
Lawmakers are scrambling to finish negotiations on a bicameral multiyear transportation funding bill by Friday to prevent an interruption.
The Department of Transportation has warned that it will have to stop making payments to state and local governments for infrastructure projects if Congress does not reach an agreement on at least another temporary extension.
Lawmakers are trying to finish talks on a multiyear highway bill that would be the first transportation funding legislation to last longer than two years since 2005.
The talks began after the House passed a bill to spend up to $325 billion on transportation projects over the next six years.
But that approach differs from a six-year bill approved by the Senate over the summer. House lawmakers had rejected the Senate bill, which authorizes funding for six years but only pays for three years of spending.
Lawmakers have passed a series of temporary extensions of federal highway funding in recent years, much to the chagrin of transportation advocates who have complained that it has been a decade since Congress has passed an infrastructure bill that lasts longer than two years.
Congress has been struggling for years to come up with a way to pay for a long-term extension.
The traditional source for transportation funding is revenue collected by the federal gas tax, which is currently set at 18.4 cents per gallon. The federal government spends about $50 billion per year on roads, but the gas tax take only brings in $34 billion annually.
Congress has turned to other areas of the federal budget to close the gap, and lawmakers on the committee negotiating a potential compromise on the the highway bill are working to identify a set of offsets for the new multiyear transportation bill before it can move forward.
The Congressional Budget Office has estimated it will take about $100 billion, in addition to the annual gas tax revenue, to pay for a six-year transportation funding bill.