WASHINGTON (Reuters) – Negotiators of a massive U.S. bill that would invest up to $3.5 trillion to expand social programs and attack climate change have made progress in recent days but have not yet brought a deal, U.S. Senate Majority Leader Chuck Schumer said on Monday.

“Over the last weekend I held many productive conversations” with lawmakers and the White House, Schumer, a Democrat, said. “We still have work to do,” he added. He did not provide details.

President Joe Biden was set to speak on Monday with Democratic Senator Joe Manchin, whose support for the wide-ranging legislation is key to its passage.

Manchin, a moderate from West Virginia where former President Donald Trump remains popular, has been an outspoken critic of the bill, saying it spends too much taxpayer money and contains climate change provisions that would hurt his state’s coal mining industry.

With virtually no chance of winning over any of the Senate’s 50 Republicans for the bill, Democrats are employing a special “budget reconciliation” strategy that would allow them to waive a 60-vote threshold required to advance most bills in the 100-member U.S. Senate.

But all 50 Democrats would have to vote “yes” on the bill once it comes up for a vote, with Democratic Vice President Kamala Harris on hand to break any 50-50 ties. Another Democratic moderate, Senator Kyrsten Sinema, also has voiced opposition to the current bill.

Progressive (NYSE:) Democrats meanwhile have been holding firm on their demand for an aggressive approach toward reducing fossil-fuel emissions blamed for climate change and expanding social programs for children and the elderly.

House of Representatives Speaker Nancy Pelosi is aiming for passage of the social investment bill and a separate $1 trillion infrastructure bill by the end of this month.