Donald Trump will announce his choice for the Supreme Court on Tuesday, he has confirmed.

The President tweeted on Monday afternoon that he had bought forward publishing his nomination, previously set for Thursday, amid a mounting furore over his refugee ban.

His vow to replace the late Judge Antonin Scalia with a hardline conservative is credited with winning him support among evangelical Christians concerned about upcoming legal fights over gender neutral bathrooms and a business' right to turn down services for gay couples.

The nine person court is currently divided equally 4-4 along conservative versus progressive lines, with one decisive seat vacant. The President nominates his choice of candidate, typically someone in line with his political views, but they must be approved by the Senate before appointed.

Senator Chuck Schumer, the Democrats' Senate leader, has vowed to fight "tooth and nail" anyone Trump nominates who is not "mainstream".

Trump has already released a list of 21 judges as nominees and is thought to be sticking to that list.

Read our analysis of the favorites here.

Although the next appointment will tilt the balance of the crucial decision making panel, Trump's next four years as President could give him the chance to nominate another one or possibly two people to the Court.

Three judges are 78 or older including 83-year-old liberal Ruth Bader Ginsburg, whom Trump called on to resign in July after she called him a "faker".

The appointments are all lifetime positions and there is no limit to how long they can stay unless they are impeached, which last happened in 1805. Since 1970 the average tenure has been 26 years, meaning Trump's influence over American politics and judiciary could extend well beyond his term as President.

If the balance shifted to a 6-3 conservative bias, the possibility of repealing the landmark Roe Vs Wade abortion ruling could be raised.

Read our explainer on why the Supreme Court was so important for evangelicals.