WASHINGTON, July 5 (Xinhua) -- U.S. President Donald Trump said Thursday that he has narrowed his list of candidates for the Supreme Court seat held by retiring Justice Anthony Kennedy.

"I think I have it down to four people. And I think of the four people I have it down to three or two." Trump told reporters aboard Air Force One during a flight to state of Montana for a rally.

The president said he will have a decision by Sunday and announce it at the White House on Monday night.

According to reports, Trump has interviewed six candidates, namely appeals court judges Brett Kavanaugh, Raymond Kethledge, Amy Coney Barrett, Amul Thapar, Joan Larsen and Thomas Hardiman.

Trump's top contenders for the vacancy reportedly are Kavanaugh, Kethledge and Barrett.

Justice Kennedy, the court's current longest-serving member and second-oldest justice, announced last week that he is retiring.

Kennedy, 81, is widely thought to be a moderate and pivotal swing vote in the highest federal court.

Liberal advocacy groups and others are concerned that Trump's pick to fill Kennedy's seat could move the court more solidly to the right and revisit landmark rulings on abortion access, gay marriage and other issues.

It would also be the second time in two years for Trump to make a Supreme Court pick.

Trump nominated Neil Gorsuch, seen as a solidly conservative, to the court shortly after he took office early 2017. Gorsuch was confirmed by the Senate with a 54-45 vote months later.

The confirmation for Trump's second court pick is expected to be contentious, with the Senate now narrowly divided, 51-49, in favor of Republicans.