The U.S. Supreme Court looks set to overturn the historic Roe v. Wade decision that legalized abortion nationwide, according to a leaked draft opinion published by Politico on Monday that sent shock waves through the country.

"Roe was egregiously wrong from the start," conservative Justice Samuel Alito wrote in the draft majority opinion dated February 10, according to Politico, which posted a copy online.

Based on Alito's opinion, the court would find that the 1973 Roe v. Wade decision – which allowed abortions to be performed before a fetus was viable outside the womb, between 24 and 28 weeks of pregnancy – was wrongly decided because the U.S. Constitution makes no specific mention of abortion rights.

"The Constitution does not prohibit the citizens of each state from regulating or prohibiting abortion," Alito said, according to the leaked document.

The unprecedented leak from the conservative-majority Supreme Court drew strong reactions throughout the country, not least because the court prides itself on keeping its internal deliberations secret and leaks are extremely uncommon.

Abortion is one of the most divisive issues in U.S. politics.

The news also comes a little more than six months before midterm elections that will determine if Democrats hold their razor-thin majorities in Congress for the next two years.

"This decision is a direct assault on the dignity, rights, & lives of women, not to mention decades of settled law," former Secretary of State Hilary Clinton tweeted in reaction to the news. 

"It will kill and subjugate women even as a vast majority of Americans think abortion should be legal. What an utter disgrace."

Republican Senator Tom Cotton said: "Roe was egregiously wrong from the beginning & I pray the Court follows the Constitution & allows the states to once again protect unborn life."

The Supreme Court, which has a 6-3 conservative majority, heard oral arguments in December on the state of Mississippi's bid to revive its ban on abortion starting at 15 weeks of pregnancy, a law blocked by lower courts.

After an initial vote among the justices following an oral argument, one is assigned the majority opinion and writes a draft. It is then circulated among the justices.

At times, the vote alignment can change before the ruling is released. A ruling is only final when it is published by the court.

According to Politico, four of the other Republican-appointed justices – Clarence Thomas, Neil Gorsuch, Brett Kavanaugh and Amy Coney Barrett - voted with Alito.

Christian conservatives and many Republican officeholders have long sought to overturn Roe v. Wade, which recognized that the right to personal privacy under the U.S. Constitution protects a woman's ability to terminate her pregnancy.

If Roe is overturned, abortion is likely to remain legal in liberal states: more than a dozen states currently have laws protecting abortion rights. Meanwhile, numerous Republican-led states have passed various abortion restrictions in defiance of Roe.

Republicans could try to enact a nationwide abortion ban, while Democrats could also seek to protect abortion rights at the national level.

(With input from Reuters)