By Jarrett Renshaw, Jeff Mason and Timothy Gardner

WASHINGTON (Reuters) – Congressional Democrats and the White House scrambled on Wednesday to find agreement on measures to tackle climate change as part of President Joe Biden’s centerpiece spending legislation ahead of coming UN climate talks in Glasgow, Scotland.

Democrats have negotiated for weeks over a spending bill on social and climate programs that, among other things, will invest in cleaner energy. But certain proposals, such as a plan to reward utilities that invest in renewable fuels and penalize those that do not, are opposed by centrist West Virginia Democrat Joe Manchin.

Instead, Democrats are considering a flurry of options, including boosting production tax credits for nuclear power and enhancing credits for carbon sequestration projects, according to three congressional sources involved in the discussions.

Biden has become more involved in the talks in recent days to try to get the legislation across the finish line.

Biden told lawmakers on Tuesday that he wants agreements on both the bipartisan infrastructure bill and the wider spending bill ahead of the UN talks. “He was very clear that is the deadline he cares most about, is having something to take to Glasgow,” one source said.

Biden told lawmakers he thought he could get Manchin and Senator Kyrsten Sinema, another centrist Democrat, to agree to a spending bill in the range of $1.75 trillion to $1.9 trillion, down from $3.5 trillion, the source said.

Manchin’s vote is needed in the 50-50 Senate for the spending bill Democrats are trying to pass on a simple majority. But Manchin has opposed a $150 billion Clean Energy Payment Plan, or CEPP, backed by Biden to reward power utilities for investments in renewable energy. West Virginia is a major producer of fossil fuels coal and .

Manchin also said this week that a carbon tax is in not in play, a mechanism backed by several Democrats in the Senate.

His office did not immediately respond to a request for comment.

Biden floated putting $300 billion toward tax incentives for solar and wind and electric vehicles, one of the sources added. Then, instead of $150 billion for the Clean Energy Payment Plan that Manchin opposed, that amount would go to nuclear energy and carbon capture and storage.

The source said he did not think that alternative would be acceptable to some progressive Democrats. “That has to be worked out,” he said.

Boosts for hydrogen production were also being debated, two of the congressional sources said. Democrats are also considering providing block grants to states to encourage more green energy production, the sources said.