WASHINGTON: US President Donald Trump on Saturday urged Republican lawmakers to back his upcoming nomination for the Supreme Court "without delay" as the issue roiled the election campaign.

Justice Ruth Bader Ginsburg, a liberal stalwart, died Friday, opening a crucial vacancy on the court and setting off a fierce political battle before the November 3 vote.

Trump tweeted that the "most important" decision that Republicans had been elected to make was "the selection of United States Supreme Court Justices."

"We have this obligation, without delay!" he added.

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

Democrats have demanded a delay in the nomination until after the election -- an uphill battle given the control Republicans have in the Senate, which must approve the president's nominee.

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