The infrastructure package pieced together by a bipartisan group of senators would create a “Carbon Reduction Program” for transportation emissions.

Transportation is the nation’s biggest source of climate-warming carbon dioxide, and the Biden administration has made addressing climate change a priority.

But the program described in the 2,702-page Senate proposal has loopholes, according to critics in the House who crafted a more comprehensive approach as part of separate infrastructure legislation passed in July. Of the hundreds of disagreements over spending and policy priorities between the two chambers, perhaps none captures the disconnect between their disparate approaches more than the two carbon reduction programs.

The Senate and House programs each set aside billions for states to use to cut emissions: $6.4 billion and $8.3 billion, respectively. The House plan would require states to meet specific emissions goals they set by tracking current emissions and future reductions, while the Senate program would have no such requirement. Instead, the Senate plan would provide funding and require that states draw up a strategy to reduce emissions, but would have no consequences if they don’t. (The House program would include regular reports on how states are performing, and would require states to shift some of the other federal funds they receive to emissions reductions if progress is not sufficient.)

It’s a reflection of partisan disagreements over how to address climate change, with many Republican lawmakers opposed to urgent action, arguing that the threat is overblown or the economic costs are too great.

The House proposal, which was years in the making, sought to fundamentally shift the status quo in the nation’s transportation-funding system to address climate change over decades. The bipartisan Senate plan, drafted quickly this summer, stitched together provisions already passed by Senate committees and sought to avoid issues that could sink an emerging deal.

The Biden administration and senators supporting the agreement say historic investments in transit and rail as part of the roughly $1 trillion package would make inroads in addressing climate change while investing in roads, replacing lead water pipes and increasing broadband access.

Critics say the investments would address climate change but are insufficient in tackling the scope of the problem.

“While the bill contains some nice progressive wins, or climate wins, those are dwarfed by the sheer magnitude of the highway construction money,” said Kevin DeGood, director of infrastructure policy at the liberal advocacy group Center for American Progress. “If I’m looking back in history, then I say, ‘Look at how much we’re spending on transit. Look at these green provisions we’ve put in this bill.’ But if I’m actually looking at the scale of the challenges we face and how rapidly climate destruction is going to occur, then I would have to say … this is inadequate to the task at hand.”

House Transportation Committee Chairman Peter A. DeFazio (D-Ore.) oversaw the drafting of the House legislation and has been leading efforts to push the Senate to adopt some of its key provisions.

DeFazio’s effort has met resistance, with Senate negotiators wary of major changes that would upset what they say is a carefully calibrated package.

“From what I’ve seen, these transformational policies were not included in the Senate’s bipartisan bill, and I remain committed to fighting for them in any final infrastructure legislation that Congress passes,” DeFazio said in a statement, noting changes to existing transportation funding programs and new initiatives to reduce carbon pollution.

In a joint statement accompanying the Senate proposal, the bipartisan group of 10 senators leading the effort noted a frenzied final stretch of work to win agreement to “invest in our nation’s hard infrastructure and create good-paying jobs for working Americans in communities across the country without raising taxes.”

The group’s members said they would get the legislation through the Senate. “This bipartisan bill and our shared commitment to see it across the finish line is further proof that the Senate can work,” they wrote.

The Carbon Reduction Program in the Senate legislation offers areas where states could spend money under the program. They include traffic management, transit systems, bike and pedestrian projects, energy-efficient street lighting, efforts to reduce peak travel, work to cut the environmental impact of hauling freight, and using zero-emission vehicles.

It also says states can use funds under the program for various other projects if the transportation secretary certifies “the State has demonstrated a reduction in transportation emissions — (A) as estimated on a per capita basis; and (B) as estimated on a per unit of economic output basis.” Senators involved in crafting that provision did not respond to requests for comment Tuesday about how economic output would be defined or is intended to work.

The House “Carbon Pollution Reduction” program would require states to set goals for reducing their emissions and would not allow states to transfer the funds for non-environmental uses; the Senate would allow up to 50 percent of the funds for uses beyond emissions.

The House bill is simpler and more demanding. It would allow spending by states as long as that spending “is expected to yield a significant reduction in greenhouse gas emissions from the surface transportation system” and “will help a State meet the greenhouse gas emissions performance targets.”