Congressional Democrats are planning to pursue a massive expansion of Medicare as part of President Biden’s new $1.8 trillion economic relief package, defying the White House after it opted against including a major health overhaul as part of its plan.

The early pledges from some party lawmakers, led by prominent members of its liberal wing, threaten to create even more political tension around a package that is already facing no shortage of it. The expansion push comes as Biden on Wednesday stressed in his first address to Congress that he is still committed to making health care more affordable.

They specifically aim to lower the eligibility age for Medicare to either 55 or 60, expand the range of health services the entitlement covers and grant the government new powers to negotiate prescription drug prices. Party lawmakers say their approach could offer new, improved or cheaper coverage to millions of older Americans nationwide.

Roughly 100 House and Senate Democrats led by Rep. Pramila Jayapal (Wash.) and Sen. Bernie Sanders (I-Vt.) publicly had encouraged Biden in recent days to include the overhaul as part of his latest package, known as the “American Families Plan,” which proposes major investments in the country’s safety net programs. Yet Biden opted only to propose additional subsidies for Americans who purchase their health insurance, disappointing many lawmakers who still otherwise support the White House’s blueprint.

Sanders said Wednesday he would “absolutely” pursue a Medicare expansion as lawmakers begin to translate Biden’s economic vision into legislation. Sen. Ron Wyden (D-Ore.), the chairman of the tax-focused Finance Committee, similarly pledged that he would “look at every possible vehicle” to lower drug costs.

And Sen. Richard J. Durbin (Ill.), the Democrats’ vote-counter in the chamber, said he planned to push for Medicare reforms he saw as a “game changer.” Durbin said he didn’t know why the White House ultimately chose to exclude the policies, but he predicted tough work ahead for Democratic leaders in crafting a legislative package that has sufficient support.

“I don’t presume that we have a majority going in,” Durbin said. “I think we have to listen carefully to all the members and particularly those who have some problems, trying to resolve [them].”

The early efforts reflect a broader belief among congressional Democrats that they must more aggressively seize on their narrow but powerful majorities to push policies that long have been stalled in Washington — no matter their cost. Many party lawmakers have pushed Biden at times to spend sky-high sums, sometimes even more than the president himself says he supports, arguing that they have a political mandate to pursue vast economic change.

But health-care revisions are likely to present a significant challenge, threatening to open rifts not just between the two parties but within the Democratic caucus itself. In an early sign of trouble, Sen. Joe Manchin III (D-W.Va.) told The Washington Post on Wednesday that he opposes expanding Medicare eligibility even as he supports broader adjustments to the Affordable Care Act.

“No, I’m not for it, period,” Manchin said when asked about efforts to expand the health-care entitlement.

Rethinking Medicare also risks touching off a fierce lobbying barrage on the part of health insurers and pharmaceutical giants, which have mobilized aggressively against such changes in the past. The corporate opposition could add to new political obstacles now facing one of the staple elements of Biden’s economic agenda.

In his address to Congress late Wednesday, Biden described his American Families Plan as a “once-in-a-generation” series of federal investments. And he specifically promised “in addition” to that package that he would try to lower health insurance premiums, reduce drug costs and pursue other reforms to the Affordable Care Act “this year.”

“This is all about a simple premise: Health care should be a right, not a privilege in America,” the president said in his address.

The families package as proposed touches on wide swaths of the economy: It endorses universal prekindergarten for all children, two years of tuition-free community college for adults, and hundreds of billions of dollars toward combating child poverty and improving child care nationwide.

The roughly $1.8 trillion blueprint follows weeks after Biden put forward a $2.3 trillion infrastructure proposal, recommended a $1.5 trillion budget for the 2022 fiscal year and secured the passage of a $1.9 trillion coronavirus stimulus bill. The raft of new federal spending evinces the White House’s philosophy that a bigger and better-funded federal government can tackle challenges ranging from the coronavirus pandemic to child poverty.

The spending has drawn staunch opposition from Republicans. Despite adding trillions to the federal deficit under President Donald Trump, GOP lawmakers blasted Biden on Thursday for seeking to spend such sizable amounts — and for trying to couple the spending with proposed tax increases on wealthy families and profitable corporations.

“Instead of empowering all kinds of families with flexibility, this one would just subsidize specific paths that Democrats deem best, so Washington can call the shots from early childhood through college graduation,” said Senate Minority Leader Mitch McConnell (Ky.), describing Biden’s latest package as “another gigantic tax-and-spend colossus.”

Combined with Biden’s stimulus and infrastructure plans, Sen. Susan Collins (R-Maine) said the total price tag of the president’s agenda also threatened to “ignite inflation, which is very harmful to our economy and American families.”

Manchin, a closely watched swing vote in virtually all significant policy fights in the Senate, also expressed some trepidation this week about tax increases outlined by Biden, including roughly a doubling of the capital gains tax rate for those earning more than $1 million per year.

“That’s a heavy lift,” Manchin said. “We just can’t make ourselves noncompetitive. We have an economy that’s ready to take off and boom. We can’t put the brakes on it.”

Most other Democrats, however, did not seem deterred — and some of the party’s leading lawmakers instead said the White House should seize on its rare opportunity to pursue even larger investments across the economy as part of the new families plan.

“This is our chance to do big things on housing, and big things on infrastructure, and big things on poverty,” Sen. Sherrod Brown (D-Ohio), the chairman of a key committee that oversees housing, told reporters Wednesday.

For many Democrats, the most enticing target is Medicare, as they try to deliver on their 2020 campaign promises to make health insurance affordable and available. Biden himself endorsed a policy report after the party’s presidential primaries — part of a “unity” effort among Democratic contenders, including Sanders — that called for lowering the Medicare enrollment age and expanding the health services it covers.

But Biden opted against including any of those provisions as part of the American Families Plan on Wednesday, choosing instead to focus on extending the additional health insurance tax benefits that Congress previously adopted as part of the most recent coronavirus stimulus. The White House pointed as part of the plan to the president’s past support for a major expansion of Medicare that would lower the eligibility to age 60 and allow the government to negotiate drug costs.

Asked about the approach, a White House official said the administration had embarked on an outreach campaign in the Capitol. The aide, who spoke on the condition of anonymity, said Vice President Harris has been phoning lawmakers to get their views on the American Families Plan.

Speaking at a press conference on Thursday, House Speaker Nancy Pelosi (D-Calif.) acknowledged “big interest in our caucus” particularly in Medicare reforms that aim to lower drug prices. But she declined to outline a path forward, saying: “What is in one bill or another is not really important.”

Other Democrats pledged to address the priorities in tandem. Sanders, who had lobbied Biden before the release of his plan, said this week that lawmakers are working “very hard” to ensure the inclusion of a Medicare expansion. His comment came just hours after he unveiled a government study that showed Americans pay between two and four times more for prescription drugs than citizens of other countries.

Citing the new data, Rep. Frank Pallone Jr. (D-N.J.), the chairman of the House Energy and Commerce Committee, also pledged to use his powerful gavel to turn to the issue in the coming weeks — stressing that tackling drug costs remains “one of my top priorities as we work to pass the American Families Plan.”

Jayapal, the leader of the Congressional Progressive Caucus, said Democrats across the Capitol are likely to intensify their political push in the coming weeks out of a belief that the president’s families plan is the most efficient route to improve Medicare — given the shrinking congressional calendar and the growing need for an overhaul.

“If we have to spend all the way through August working on the jobs and families plan[s], I don’t think we have the time,” Jayapal said about calls to tackle Medicare independently. “Everything gets harder heading into the midterms.”