The battle over health care is back.

The Trump administration on Monday supported the full dismantling of the Affordable Care Act, even as Democratic leaders in the House introduced legislation Tuesday to strengthen the health care law.

The Justice Department said in a filing with the 5th U.S. Circuit Court of Appeals that a lower court judge's ruling should be affirmed and the entire law invalidated.

In December, Judge Reed O'Connor of the U.S. District Court in Fort Worth, Texas, ruled the law's individual mandate "can no longer be sustained as an exercise of Congress’s tax power” and that the remaining portions of the Affordable Care Act, also known as Obamacare, are void, too. O'Connor based his decision on changes to U.S. tax code passed by Republicans in 2017.

The Trump administration said in the filing, which was signed by three Justice Department attorneys, that it planned to file a brief in support of a Texas-led group of states seeking to have the entire law struck.

The filing comes as Democrats try to fulfill campaign promises about health care — an issue that they gave primary importance in the midterm elections last year.

The bill unveiled Tuesday would make more middle-class people eligible for subsidized health insurance through former President Barack Obama's health care law while increasing aid for those with lower incomes who already qualify, House Speaker Nancy Pelosi's office told The Associated Press. The legislation would also fix a longstanding affordability problem for some consumers, known as the "family glitch."

The legislation would provide money to help insurers pay the bills of their costliest patients and restore advertising and outreach budgets slashed by Trump's administration, helping to stabilize health insurance markets, the AP reported. It would also block the administration from loosening "Obamacare" rules through waivers that allow states to undermine protections for people with pre-existing medical conditions or to scale back "essential" benefits like coverage for mental health and addiction treatment.

The bill will get a vote in the House, but as a package it has no chance of passing the Republican-controlled Senate. However, some elements have bipartisan support and may make it into law.

The action on health care comes as the government said Monday that 11.4 million people have signed up for health care coverage through the Affordable Care Act this year, a slight dip from 2018, the AP said.

The Centers for Medicare and Medicaid Services found remarkably steady enrollment, down only about 300,000 consumers, according to the AP. Premiums stabilized, and more insurers came into the market. But the number of new customers fell by more than 500,000 — a worrisome sign for Obamacare backers, who say the Trump administration's cuts to the ad budget and congressional repeal of a requirement that people get insured will gradually eat away at program enrollment.

Responding to the Justice Department's legal filing, Pelosi, D-Calif., said in a statement that the Trump administration "decided not only to try to destroy protections for Americans living with pre-existing conditions, but to declare all-out war on the health care of the American people."

During a press conference for the unveiling of the Democratic legislation, Pelosi slammed the Trump administration and Republican lawmakers who want to repeal Obamacare.

"Martin Luther King talks about of all the injustices, the most inhumane is the inequality of health care," Pelosi said. "And the Department of Justice becomes the department of injustice when it wants to tear down health care benefits because, as Dr. King said, people could die. People could die. In this House, with a Democratic majority, we’re here to strengthen those protections and to lower health care cost further because this House, this Democratic House, is for the people."

Senate Minority Leader Chuck Schumer, D-N.Y., tweeted earlier Tuesday: "I thought @realDonaldTrump & AG Barr couldn’t stoop any lower in trying to take health care away. But now they say millions gaining access to health care or protecting pre-existing conditions is unconstitutional. We will keep fighting to stop them."

Health care was the main subject of discussion at a policy lunch President Donald Trump attended with GOP senators Tuesday.

Asked before the lunch what his message would be to Americans concerned about their coverage, Trump said: "The Republican Party will soon be known as the party of health care. You watch."

Sen. Lindsey Graham, R-S.C., said outside the lunch that Trump is focusing on health care because of its importance during last year's election and the likelihood it will continue to be a major issue in 2020.

Sen. Kevin Cramer, R-N.D., said Trump provided few details on a new health care plan except that he wanted it to include protections for pre-existing conditions and health care block grants for states.

Trump and dozens of GOP lawmakers had pledged during last fall's campaigns to protect coverage for pre-existing conditions.

A recent Fox News poll found that just 37 percent of registered voters approve of President Donald Trump's handling of health care compared with 52 percent who disapprove.