A key Republican in the bipartisan Senate group working on a $579 billion infrastructure package said disagreements over transit funding and revenue sources that have held up a deal should be settled and legislative language agreed to by early next week.

“We’re working through today and through the weekend,” Louisiana Senator Bill Cassidy said Friday on Bloomberg Television’s “Balance of Power With David Westin.” “We hope to have language either by Monday or by early next week.”

Cassidy said the group of 22 senators is close to reaching agreement on how to pay for transportation, broadband, water systems and other pieces of the nation’s infrastructure in the proposal.

The latest hangup has been funding for mass transit systems. Some Republicans want to reduce future highway trust fund disbursement for rail and bus systems to 18% from 20% of transportation funding that’s primarily funded by the gas tax, in light of the bill’s large overall boost for transit. But Democratic Senators Sherrod Brown of Ohio and Tom Carper of Delaware said in a Thursday letter that they won’t vote for a bill that “neglects this fundamental part of our nation’s infrastructure.”

“Yeah, there’s some problems with transportation—with transit in particular—but on the other hand, we can find a solution,” Cassidy said.

At the White House, Press Secretary Jen Psaki noted that President Joe Biden has said transit funding is “extremely important to the president, the Amtrak president.”

Biden has had conversations with lawmakers and is available to talk throughout the weekend and in the coming weeks, Psaki said.

“The door to the Oval Office is always open,” she added.

Cassidy said senators should be prepared to delay their scheduled August recess to finish work on the package. Majority Leader Chuck Schumer has indicated that he is prepared to keep members past Aug. 9 to finish work on both the bipartisan infrastructure bill and a budget resolution teeing up a separate $3.5 trillion package that would fund most of Biden’s economic agenda.

“I think this package is so good for the American people that I’m willing to give up some of my recess if we can get this done,” Cassidy said.