WASHINGTON (AP) — President Joe Biden’s hopes of channeling billions of dollars into green infrastructure investments to fight climate change are running into the political obstacle of winning over Republican lawmakers who oppose that approach as unnecessary, excessive spending.

As negotiations unfold in Congress in search of a bipartisan deal, the White House's ability to ensure a climate focus in Biden's sweeping infrastructure package is becoming daunting — so much so that key Democrats are warning the administration to quit negotiating with Republicans, calling it a waste of time that will produce no viable compromise.

“From my perspective, no climate, no deal,” said Sen. Ed Markey, D-Mass. “I won’t just vote against an infrastructure package without climate action — I’ll fight against it.″

The debate is similar to the political and policy differences complicating Biden’s broader talks over his ambitious infrastructure agenda, the sweeping $1.7 trillion American Jobs Plan making its way through Congress, as Democrats and Republicans argue over what, exactly, constitutes infrastructure and how much is needed.

The White House is holding firm to Biden's initial ideas, which tally nearly $1 trillion in climate-related investments that aim to bolster the electric vehicle market, make buildings and property more resilient to harsh weather patterns and push the country's electrical grid to become carbon-free by 2035.

The president is seeking a newer definition of infrastructure, trying not only to patch up the nation’s roads and highways, but also to rebuild its economy with new kinds of investments for the 21st century. The Republicans prefer a more traditional approach that touches modestly on some climate-related elements but focuses more specifically on transportation and other typical developments.

As Biden courts a new bipartisan group of 10 senators, who are eyeing a scaled-down proposal, leading Democrats are worried their party is losing an opportunity with control of the House, Senate and White House to make gains on its climate change priorities.

“The President has underscored that climate change is one of the defining crises we face as a nation," White House deputy press secretary Andrew Bates said Friday, "and he and his team have continuously fought for leading on the clean energy economy and on clean energy jobs – which is critical for our economic growth, competitiveness, and middle class.”

At a climate forum Friday, former Vice President Al Gore, who spoke to Biden last month, said: “I know he is committed to this issue. I know it very well because he knows and has said inaction is simply not an option."

For all the divisions, there may be some common ground between the White House and the Republicans, particularly with the GOP senators now engaged in bipartisan talks.

Republican Sen. Bill Cassidy of Louisiana, a lead GOP negotiator, said he brought up flood resiliency and energy provisions that would benefit his state during a call with Biden on Tuesday. He was also seen engaged in a lengthy and somewhat animated conversation with Biden on the tarmac last month when the president visited Louisiana.

Hailing from a coastal state familiar with the hazards of harsh weather, Cassidy supports a bipartisan bill to offer tax breaks to property owners that protect homes and businesses against natural disasters such as wildfires, hurricanes, floods and drought, and another to support projects that ”capture” and store carbon dioxide produced by coal-fired plants and other fossil fuels. Louisiana has several sites vying to become a national hub for carbon capture.

Senate Republican leader Mitch McConnell has been largely silent on the bipartisan effort, and other GOP leaders are cool to this latest negotiation, doubtful their five Republican colleagues will find a compromise.

Sen. John Barrasso of Wyoming, the No. 3 in Republican leadership, told reporters, “The things you’re going to need to do to get Democratic votes, it'd be hard to get any Republicans.”

With the Congress narrowly split, and the Senate evenly divided, 50-50, Biden would need support from at least 10 Republicans to reach the 60-vote threshold required to break a filibuster by opponents. The president is encouraging Democrats to also launch a parallel track using budget reconciliation rules that would allow passage with 51 votes, achievable because Vice President Kamala Harris can cast a tiebreaking vote.

Still, the White House and Republicans remain far apart on key details, including the overall scope of the package and how to pay for it.

Biden wants to hike the corporate tax rate, from 21% to 28%, which Republicans oppose as a red line they will not cross.

Instead, the emerging bipartisan proposal from the 10 senators is expected to include an increase in the federal gas tax, which consumers pay at the pump, by linking it to inflation. Biden rejects that approach because he refuses to raise taxes on anyone making less than $400,000 a year. The group also may tap unspent COVID-19 relief funds and go after unpaid income taxes.

Jamal Raad, executive director of Evergreen Action, an environmental group, said after months of negotiations that “it’s clear there will never be 10 votes from the GOP caucus” for major investments like those proposed by the White House.

In the House, the Congressional Progressive Caucus' Rep. Ro Khanna, D-Calif., tweeted: “An infrastructure bill that doesn’t prioritize the climate crisis will not pass the House. Period.”

And Sen. Sheldon Whitehouse, D-R.I., a leading climate hawk, said he is “nervous” that Democrats may not be serious about addressing climate change in the infrastructure bill. “We are running out of time.’’

Biden administration officials say they understand the concerns. White House climate adviser Gina McCarthy said she and other officials “are going to fight like crazy” to make sure provisions, including a clean electricity standard, are included in the final bill.

The standard calls for making the nation’s electricity sector carbon-free by 2035, a key aspect of Biden's goal of halving the nation's greenhouse gas emissions.

Michael Brune, executive director of the Sierra Club, said he and others are concerned about the extended effort to win over GOP votes they consider unlikely to succeed.

From his home in California, he said he sees the threat of wildfires and drought fueled by climate change on a daily basis. “We are in a dire moment, and we don’t always have leadership that reflects that," he said.

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Associated Press writer Kevin Freking in Washington to this report.