Democrats, still fuming over the Republican-led Senate`s refusal to act on former President Barack Obama`s court nominee last year, girded for a fight.
Trump has announced he will reveal his choice to replace conservative Justice Antonin Scalia, who died last February, at the White House at 8 p.m. (0100 GMT on Wednesday).
"We`ll be announcing a Supreme Court justice who I think everybody`s going to be impressed with," Trump told reporters at a cyber security event in the White House.
The court is ideologically split with four conservative justices and four liberals, and Trump`s pick can restore its conservative majority.
A source involved in the selection process said Trump had made his choice between two conservative U.S. appeals court judges - Neil Gorsuch and Thomas Hardiman. Both were appointed to the bench by former Republican President George W. Bush.
CNN, citing an unnamed source, said Gorsuch, a judge on the Denver-based 10th U.S. Circuit Court of Appeals, had been told he was the likely nominee.
Adding an element of drama to what is normally a sober announcement, CNN said both Gorsuch and Hardiman, who serves on the Philadelphia-based 3rd U.S. Circuit Court of Appeals, had been brought to Washington ahead of Tuesday`s announcement.
The White House ratcheted up the tension by sending a statement calling on Americans to watch the decision live on Facebook. "You won`t want to miss it!" the statement said.
A senior Senate Republican aide said Majority Leader Mitch McConnell had already been informed of Trump`s pick, which the senator described as an "outstanding choice."
Under the Constitution, a president`s Supreme Court nomination requires Senate confirmation.
Trump set to name conservative judge as US Supreme Court pick
01 February 2017
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President Donald Trump was set to unveil his pick on Tuesday for a lifetime job on the U.S. Supreme Court, likely choosing a conservative judge to try to shape the court for years to come on issues like abortion and gun and religious rights, Reuters reported.
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