WASHINGTON — President Donald Trump signed an executive order Thursday calling for the dismantling of the U.S. Education Department, advancing a campaign promise to take apart an agency that’s been a longtime target of conservatives.

Trump has derided the Education Department as wasteful and polluted by liberal ideology. However, completing its dismantling is most likely impossible without an act of Congress, which created the department in 1979. Republicans said they will introduce legislation to achieve that, while Democrats have quickly lined up to oppose the idea.

The order says the education secretary will, “to the maximum extent appropriate and permitted by law, take all necessary steps to facilitate the closure of the Department of Education and return authority over education to the States and local communities.”

It offers no detail on how that work will be carried out or where it will be targeted, though the White House said the agency will retain certain critical functions.

Trump said his administration will close the department beyond its “core necessities,” preserving its responsibilities for Title I funding for low-income schools, Pell grants and money for children with disabilities.

The White House said earlier Thursday the department will continue to manage federal student loans, but the order appears to say the opposite. It says the Education Department doesn’t have the staff to oversee its $1.6 trillion loan portfolio and “must return bank functions to an entity equipped to serve America’s students.”

At a signing ceremony, Trump blamed the department for America’s lagging academic performance and said states will do a better job.

“It’s doing us no good,” he said.

Already, Trump’s Republican administration has been gutting the agency. Its workforce is being slashed in half, and there have been deep cuts to the Office for Civil Rights and the Institute of Education Sciences, which gathers data on the nation’s academic progress.

Education Secretary Linda McMahon said she will remove red tape and empower states to decide what’s best for their schools. But she promised to continue essential services and work with states and Congress “to ensure a lawful and orderly transition.”

Part of her job will be exploring which agencies can take on the Education Department’s various roles, she said.

“The Department of Justice already has a civil rights office, and I think that there is an opportunity to discuss with Attorney General Bondi about locating some of our civil rights work there,” McMahon told reporters after the signing.

The measure was celebrated by groups that have long called for an end to the department.

“For decades, it has funneled billions of taxpayer dollars into a failing system — one that prioritizes leftist indoctrination over academic excellence, all while student achievement stagnates and America falls further behind,” said Kevin Roberts, president of the Heritage Foundation.

Advocates for public schools said eliminating the department would leave children behind in a fundamentally unequal education system.

“This is a dark day for the millions of American children who depend on federal funding for a quality education, including those in poor and rural communities with parents who voted for Trump,” NAACP President Derrick Johnson said.

Opponents are already gearing up for legal challenges, including Democracy Forward, a public interest litigation group. Senate Minority Leader Chuck Schumer, D-N.Y., called the order a “tyrannical power grab” and “one of the most destructive and devastating steps Donald Trump has ever taken.”