WASHINGTON, United States (AFP) — US President Donald Trump plans to announce his Supreme Court nominee Tuesday, seizing an opportunity to tilt the bench to conservatives on crucial issues such as abortion and gun control.

Trump’s choice is meant to fill a vacancy left by the sudden death of conservative justice Antonin Scalia almost one year ago that left the highest US court evenly divided between four conservative and four liberal justices.

The outcome of the “very big decision,” due to be announced at 8:00 pm (0100 GMT Wednesday) at the White House, is an “unbelievably highly respected” candidate, Trump told reporters.

The announcement — two days ahead of schedule and scheduled for prime television viewing time — sets the stage for what is certain to be a bruising battle with Democrats.

They are still smarting from the loss of the White House and Republicans’ refusal to consider — much less vote on — former president Barack Obama’s nominee for the same Supreme Court seat.

Abortion, gay marriage and gun control are just some of the hot button issues of American life and law on which the Supreme Court is the final arbiter.

Its members, who must be confirmed by the Senate, are named to life terms.

Given the advanced age of several sitting justices, Trump could potentially make several appointments to the court during his term, giving him the opportunity to shape its direction for a generation.

Once confirmed, Supreme Court justices enjoy absolute independence, however, and some have proved to be politically unpredictable, which sharply raises the stakes of the Senate confirmation process.

Trump has said he wants a candidate who is against abortion and firmly backs Americans’ right to own guns.

In a presidential debate in October, the billionaire Republican said his Supreme Court picks would “automatically” lead to overturning Roe v Wade, the emblematic 1973 ruling that legalized abortion in the United States.

Among those tipped as frontrunners for the post are: Neil Gorsuch, 49, a respected appellate court judge who is considered an ideological match to Scalia and takes a broad view of religious freedom; William Pryor, 54, an appellate court judge and former Alabama attorney general seen as an opponent of abortion rights; and Thomas Hardiman, 51, an appellate court judge with a record as a defender of gun rights, police powers and the rights of local governments to display the Ten Commandments.

Trump had said he would announce his pick on Thursday, but then moved the date up amid a raging controversy over his order to temporarily bar refugees and travelers from seven predominantly Muslim countries from entering the United States.

Four federal judges issued temporary orders blocking deportations of people detained at US airports, embroiling the fledgling administration in its first major legal challenges, with advocates vowing to take the fight to the Supreme Court.

Chuck Schumer, the Senate minority leader, has vowed to fight “tooth and nail” if Trump puts forward a Supreme Court nominee unacceptable to Democrats, as is likely to be the case.

Republicans hold 52 seats in the Senate but need 60 to confirm a nominee, which means Trump’s choice must be someone capable of winning at least some Democratic votes.

That may prove an arduous task in the current political climate.

“That just shows you that it’s all about politics, it’s not about qualification,” White House spokesman Sean Spicer told a press conference. “The president has a right to have his nominees taken up.”

However, Spicer did not mention the fact that Obama had chosen Merrick Garland, an appellate court judge with a reputation as a moderate, to win over Republicans, who nonetheless refused to take up the nomination for nearly a year.

In doing so, Republicans deeply antagonized Democrats, though they reaped the ultimate prize with Trump’s election.

Garland earlier this month withdrew his name from consideration and returned to his old job as chief judge of the US Court of Appeals for the District of Columbia Circuit in Washington.