The United States House of Representatives is expected to vote this week on whether to remove the ratification deadline for the Equal Rights Amendment (ERA), which would grant equal rights to all US citizens regardless of sex.

Congress imposed a deadline when it first proposed the amendment in 1972. But the deadline expired nearly four decades ago after only 35 states had agreed to the amendment. Constitutional amendments must be ratified by at least 38 states.

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Democrats in the House now plan to approve a resolution that would remove the deadline altogether. The Republican-led US Senate would have to agree, which is unlikely.

The proposed amendment gained new life when Virginia became the 38th state to ratify the amendment on January 27 after Democrats took control of the state legislature for the first time in 27 years.

As the ERA comes into the national spotlight again, here is a look at what it is and why some say it is so important.

What is the Equal Rights Amendment?

Advocates for gender equality in the US have been pushing for an amendment to the US Constitution that would provide for equal rights between men and women for nearly a century.

The ERA was first proposed in 1923 by Alice Paul, leader of the National Woman's Party, soon after ratification of the 19th Amendment which gave women - though, in reality, only white women at the time - the right to vote in the US.

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It was not until 1972 that Congress approved an updated wording of the proposed amendment by votes of more than two-thirds majorities in both the House and Senate.

The ERA reads: "Equality of rights under the law shall not be denied or abridged by the United States or any State on account of sex", and Congress shall have the power to enforce that right.

What would the ERA do?

The ERA would provide a fundamental legal remedy against gender discrimination for both women and men, according to the Alice Paul Institute, a non-profit group dedicated to ratifying the ERA.

The ERA would affect judicial handling of a wide range of claims including matters of workplace discrimination, gender identity, sexual harassment, domestic abuse and reproductive rights.

US courts have dealt inconsistently of sex discrimination and, under the ERA, any laws containing the different treatment of men and women would be subject to strict scrutiny.

The amendment would further serve as a pre-emptive warning to any legislators seeking to write new laws that would treat men and women unequally.

Why are some people against it?

Opposition to the ERA has come from conservatives who argue it would spawn a wide range of unintended lawsuits that would degrade women's status.

The late conservative activist Phyllis Schlafly campaigned against the ERA in the 1970s, arguing it would deprive women of their special protections and privileges.

Phyllis Schlafly, a long time foe of the Equal Rights Amendment addresses her supporters at a rally at the State Capitol on November 22, 1977, in Springfield, Illinois [File: AP Photo]

Opponents argue the ERA would hurt families and strip women of certain privileges, such as separate bathrooms and Social Security benefits for widows, among others. Attention in recent years has turned specifically to abortion, with opponents of the ERA warning that the amendment is "abortion in disguise".

Proponents argue that reproductive rights must be part of the conversation, but according to the Alice Paul Institute, "the ERA does not add new laws to the US Constitution, it only guarantees the rights currently within it. Issues like abortion, same-sex marriage, unisex bathrooms, and the female draft exist separately from the ERA and would not become law upon the ERA's passage."

Public opinion surveys have suggested broad public support for the ERA. A 2016 survey commissioned by the ERA Coalition, a pro-ERA advocacy group, found a 94 percent majority support a constitutional guarantee of equal rights for men and women.

Why is Congress talking about eliminating the deadline?

When Congress proposed the ERA, it set a 1979 deadline for ratification by the states. Congress extended the deadline to 1982.

But after Virginia's legislature gained a Democratic-majority, the debate over the ERA re-emerged.

Attorneys general for Virginia, Illinois and Nevada - the last three states to ratify the ERA - filed a lawsuit in federal court seeking to force judicial recognition of the amendment.

Supporters of the Equal Rights Amendment carry a banner down Pennsylvania Avenue in Washington, DC, on August 26, 1977 [File: AP Photo]

The Trump administration's Department of Justice issued a legal memo on January 6 arguing the ERA could not be ratified because of the expired deadline. Others have highlighted that five states - Idaho, Kentucky, Nebraska, Tennessee and South Dakota - have voted to revoke their ratifications of the ERA.

The case is likely to go to the US Supreme Court.

Supreme Court Justice Ruth Bader Ginsburg, a staunch supporter of the ERA, suggested that it may be time to restart the ERA debate altogether.

"I'd like to start it over," she said at an event at Georgetown University Law, US media reported.

Ginsberg had already said she hopes the ERA "will be put back in the political hopper, starting over again, collecting the necessary number of states to ratify it".

What has to happen for an amendment to become part of the US Constitution?

The US Constitution provides that an amendment may be proposed by Congress with a two-thirds vote in both chambers, or by a constitutional convention convened by two-thirds of the state legislatures.

A proposed amendment becomes part of the Constitution as soon as it is ratified by two-thirds of the states, or 38 of 50.

The National Archivist is then required to certify an amendment has been ratified. The archivist declined to do so following Virginia's ratification of the ERA because of the Justice Department's legal opinion citing the expired deadline.