WASHINGTON (Reuters) - The Trump administration on Wednesday said it was too late to renew the effort to push through a decades-old proposed amendment to the U.S. Constitution that would ensure American women have equal rights to men.

FILE PHOTO: A demonstrator holds a sign calling for an equal rights amendment (ERA) during in the Third Annual Women's March at Freedom Plaza in Washington, U.S., January 19, 2019. REUTERS/Joshua Roberts/File Photo

The U.S. Justice Department’s Office of Legal Counsel issued a legal opinion saying the deadline had long passed for additional states to ratify the Equal Rights Amendment, which was backed by 35 states in the 1970s, three short of the required number.

The amendment, which was first proposed in the 1920s and gained traction during the rise of the feminist movement, states in part: “Equality of rights under the law shall not be abridged by the United States or any state on account of sex.”

Under the Constitution, 38 states and both the House of Representatives and the Senate have to approve a proposed amendment for it for it to be formally adopted.

The House and Senate both supported the measure in 1972 but set a seven-year deadline, later extended until 1982, for it to be ratified.

Recently, there’s been a new effort to get three additional states to sign on. Nevada did so in 2017 and Illinois followed suit in 2018. Now, Virginia could, under the theory proposed by supporters of the amendment, become the 38th state as it is expected to vote this year.

The Democratic-controlled House Judiciary Committee voted in November to approve a measure that would retroactively remove the ratification deadline.

The opinion issued on Wednesday could provide legal ammunition for opponents as the debate plays out at the state level and in Congress.

Assistant Attorney General Steven Engel wrote in the opinion that while Congress “had the constitutional authority” to set the deadline, it cannot now reopen the issue.

“Congress may not revive a proposed amendment after the deadline has expired,” he wrote.

“Should the people of the United States wish to adopt the ERA as part of the Constitution, then the appropriate path is for Congress ... to propose that amendment once more,” Engel added.

The National Archives and Records Administration, a federal agency that has a role in certifying ratification, said in a statement that it would abide by the Justice Department opinion “unless otherwise directed by a final court order.”