WASHINGTON—Top Senate Republicans are pushing back on a Biden administration effort to discourage states from using funds in the roughly $1 trillion infrastructure law to expand highways, as a separate partisan battle over government spending slows the release of much of the public-works money.

 

In a Wednesday letter, Senate Minority Leader Mitch McConnell (R., Ky.) and Sen. Shelley Moore Capito (R., W.Va.) wrote to U.S. governors that they should ignore recent guidance from the Biden administration about how to use the funds. The two senators, who each supported the law when it passed this summer, criticized a December memo from the Biden administration encouraging states to use new funding to maintain and improve highways before they use it to add lanes.

 

The Biden administration memo “is an internal document, has no effect of law, and states should treat it as such,” Mr. McConnell and Mrs. Capito wrote.

 

The dispute over the memo comes as both parties begin jockeying to shape the use of the funds. While drafting the bill last year, some Democrats had sought to place additional requirements on states for using the federal money, including to limit the expansion of highways, in an effort to push states to invest more in forms of transportation that emit less carbon per person than traditional gasoline-powered cars, such as public transit.

 

Democrats dropped many of those provisions as they crafted a compromise bill with Republicans, and the infrastructure law left wide discretion to states over the swell of new federal funding. The infrastructure bill relied on unspent Covid-19 aid and other sources to fund much of the spending, eschewing any increase to the federal gasoline tax or a new vehicle-miles-traveled levy proposed by some lawmakers.

 

In the December memo, deputy administrator of the Federal Highway Administration Stephanie Pollack said the administration would emphasize the safety and sustainability of projects as it allocates the funds.

 

The agency will push recipients of federal highway funding to “select projects that improve the condition and safety of existing transportation infrastructure within the right-of-way before advancing projects that add new general purpose travel lanes serving single occupancy vehicles,” Ms. Pollack wrote.

 

A group of 16 Republican governors last month wrote a letter to Mr. Biden calling for states to have flexibility in how they use the funds, arguing in particular against “an attempt by the Federal Highway Administration to limit state widening projects.”

 

Much of the infrastructure law’s roughly $1 trillion in funding is still tied up in Congress. While the law authorized new programs and spending, Congress still needs to approve many of the new funds as part of the annual appropriations process.

 

But Republicans and Democrats have so far failed to agree to a new set of spending bills, instead approving a series of short-term measures that continue spending at levels from last fiscal year. Because Congress set those funding levels before it approved the infrastructure law, many state infrastructure agencies have yet to receive the major funding boosts approved in the infrastructure law.

 

“We haven’t realized any of the funding increases that were included in the infrastructure bill because Congress can’t get their act together and pass full-year appropriations bills,” said Jim Tymon, the executive director of the American Association of State Highway and Transportation Officials.

 

“States are just not able to plan their program of projects they want to accomplish this calendar year because of the unpredictability of what’s happening at the federal level,” he said.

 

The House on Tuesday passed another short-term extension, approving funding through March 11, as Republicans and Democrats continue to haggle over full-year bills for the fiscal year that started in October.

 

“We’re in a holding pattern, and it’s going to be very problematic if this doesn’t get resolved fairly soon, because you got to try and get contracts out for this construction season, which is limited in large parts of the country,” said Rep. Peter DeFazio (D., Ore.), chairman of the House Transportation and Infrastructure Committee.

 

—Ted Mann contributed to this article.