US Supreme Court Justice and liberal icon Ruth Bader Ginsburg died on Friday, opening a crucial vacancy on the high court expected to set off a pitched political battle at the peak of the presidential campaign.

Affectionately known as the 'Notorious RBG,' the 87-year-old Ginsburg was the oldest of nine Supreme Court justices.

She died after a fight with pancreatic cancer, the court announced, saying she passed away “surrounded by her family at her home in Washington, DC”.

Coming just 46 days before an election in which President Donald Trump lags his Democratic rival Joe Biden in the polls, the vacancy offers the Republican a chance to lock in a conservative majority at the court for decades to come.

Trump issued a statement praising Ginsburg as a “titan of the law,” but gave no indication whether he intended to press ahead with a nomination.

Accolades flowed in for the pioneering Jewish justice. “Our Nation has lost a jurist of historic stature,” said Chief Justice John Roberts.

Trump's predecessor Barack Obama said in a tweet that Ginsburg “fought to the end, through her cancer, with unwavering faith in our democracy and its ideals”.

Biden said she was “an American hero, a giant of legal doctrine, and a relentless voice in the pursuit of that highest American ideal: equal justice under law”.

In Washington, hundreds of tearful mourners laid flowers in front of the Supreme Court, where the diminutive Ginsburg sat for 27 years — even taking arguments and issuing opinions from her hospital bed after repeated bouts of illness over the past two years.

US flags flew at half-mast on each side of the court building. People lit candles on the steps of the court while others held rainbow flags.

Among the notably young crowd was Erin Drumm, a student at the Catholic University of America.

“I came here because I think RBG represents everything that America should stand for,” the 19-year-old said.

“She represents the freedom to choose and respect for science and other people regardless of their gender, race, ethnicity or religion.”

Taylor Gutierrez, 26, said he wanted to celebrate Ginsburg's achievements, “especially as a gay man knowing that she helped create a more equitable society for us."

“But I think at the same time there's just a certain trepidation since we don't really know what's going to come next,” he added.

“There's a very real fear that those things could be rolled back.”

One placard on the court steps read: “We love you Ruthie Bear”.

Ginsburg anchored the court's liberal faction, whittled to four by two Trump appointments since 2017. The appointment of a sixth conservative justice could lead to a court that would potentially remove abortion rights, strengthen the powers of business, and water down rights provided to minorities and the LGBTQ community over the past three decades.

Within minutes of the news of her death, the enormous political battle had begun — with Biden warning Trump had no right to name a successor so close to the November 3 election.

Democrats are expected to fight tough to force a delay — an uphill battle given the control Republicans have on the Senate, which must approve any nominee.

Election issue

Born in Brooklyn in 1933, Ginsburg was a law school star when women didn't study law, and a law professor with a powerful impact on the establishment of rights for women and minorities.

She died on the evening that marked the beginning of Rosh Hashanah, the Jewish New Year. According to tradition, those who die during the holiday are revered as a “tzaddik,” or a person of great righteousness.

Ginsburg's death gives Trump the opportunity to tilt the court to the right, potentially for decades, with media reporting that a new nomination could be quick.

But it also has the potential to mobilise voters on the Democratic side.

Trump said in August he would have no qualms about naming a new justice so close to the election, and last week unveiled 20 names of possible choices, all deeply conservative.

Drawing a line in the sand on Friday, Biden warned: “The voters should pick the president, and the president should pick the justice for the Senate to consider.”

“This was the position the Republican Senate took in 2016 when they were almost 10 months to go before the election. That's the position the United States Senate must take today.”

Biden was referring to Senate Majority Leader Mitch McConnell's decision in 2016, in Obama's last year in office, to block the president's court nominee so that Trump could name his own the following year. But in a statement on Friday, McConnell rejected the notion he had set a precedent.

“President Trump's nominee will receive a vote on the floor of the United States Senate,” McConnell said.

The stakes are extremely high, according to Carl Tobias, a law professor at the University of Richmond.

“The political fight will be huge because appointing a very conservative person will make this the most conservative court in a century,” he said.

According to NPR radio, Ginsburg raised the issue this week with her granddaughter Clara Spera.

“My most fervent wish is that I will not be replaced until a new president is installed,” she said.