Reps. Mo Brooks (R-Ala.), center, and Dave Brat (R-Va.), right, members of the conservative Freedom Caucus, leave Capitol Hill on Thursday to meet with President Trump. (J. Scott Applewhite/AP)

The Trump administration and House Republican leaders negotiated Thursday over demands from the chamber’s most conservative faction to tear apart the Affordable Care Act — offering to make changes far more profound than those on which lawmakers had been preparing to vote.

On Wednesday, members of the House Freedom Caucus, the far-right wing of the GOP conference, discussed with President Trump the idea of eliminating a list of 10 “essential health benefits” that the ACA requires to be covered in health plans sold to individuals and small busi­nesses. They include maternity care, mental health and addiction treatment, and services that help prevent people from getting sick and help them manage chronic diseases.

By Thursday, demands from this renegade faction of conservatives had broadened significantly. According to people briefed on the negotiations, the Freedom Caucus members met again with the president and insisted on the elimination of almost the entirety of a broad and fundamental section of the ACA.

The changes would mean that insurers could return to setting annual and lifetime limits on people’s coverage. Health plans could sell policies that exclude preventive care and immunizations. And they could charge more to customers based on their gender or genetic information, among other factors. These were all insurance practices that the ACA has outlawed for the past few years.

Although Trump was open to changes along these lines, the meeting at the White House ended without an agreement. In the afternoon, the Freedom Caucus took an internal ballot on the latest offer from the White House and House Republican leaders, and most rejected it.

(Daron Taylor/The Washington Post)

The uncustomary power the Freedom Caucus wields at the moment over the fate of the American Health Care Act, as the GOP legislation is known, became evident Thursday afternoon.

The House’s GOP leaders announced that they were postponing a vote on the legislation that had been scheduled for Thursday evening because they lacked enough support to pass it.

In holding out for deeper changes, the rebelling conservatives also want to eliminate another feature of the ACA, the part of the law that created the ACA’s insurance marketplaces — known as exchanges — for individuals and families that do not have access to affordable health benefits through a job.

The only parts of the section that the conservatives are willing to keep are two of the ACA’s most popular elements: letting young adults stay on parents’ health policies until they are 26, and forbidding insurers from denying coverage or charging more to customers with preexisting medical problems.

The essential benefits list and the broader provisions that conservatives are angling to eliminate all conflict with basic ground rules that House Speaker Paul D. Ryan (R-Wis.) had set for the first stage of Congress’s move to repeal and replace the 2010 law with a more conservative set of health-care policies. Until now, the House speaker had insisted that the legislation on which the chamber votes contain only provisions that affect federal spending and thus would fit within a special budget process called reconciliation.

Under that process, legislation can pass in the Senate by a simple majority of 50 votes, rather than the typical 60 votes needed to ward off a filibuster — a significant consideration because the Senate has 52 Republicans.

Eliminating the essential benefits and other changes advocated by the Freedom Caucus almost certainly would be ruled by the Senate’s parliamentarian as not fitting within the reconciliation rules.

The other items on the list of essential benefits that could be removed include coverage for care in doctors’ offices or other outpatient settings, emergency services, hospital care, prescription drugs and pediatric services.

When the ACA passed in 2010, congressional Democrats and members of the Obama administration said these essential benefits would guarantee that people who buy coverage on their own and small businesses would no longer be at risk of skimpy and inadequate insurance.

Conservatives, however, have long argued that Americans should be free to buy only as much coverage as they want and that allowing bare-bones health plans would lower insurance costs.