WASHINGTON (Reuters) - Conservative federal appeals court judges Brett Kavanaugh and Raymond Kethledge are the two most serious contenders being considered by President Donald Trump for the U.S. Supreme Court, a source familiar with the process said on Thursday.

FILE PHOTO: The U.S. Supreme Court is seen as the court nears the end of its term in Washington, U.S., June 11, 2018. REUTERS/Erin Schaff/File Photo

Kavanaugh serves on the U.S. Court of Appeals for the District of Columbia Circuit. Kethledge, of Michigan, serves on the Cincinnati-based 6th U.S. Circuit Court of Appeals. Both are in their early 50s and potentially could serve decades in the lifetime post on the nine-member court.

The source told Reuters that Amy Coney Barrett of Indiana, a judge on the Chicago-based 7th U.S. Circuit Court of Appeals, was still in contention but that the Republican president had been asking more questions about the other two, who have more extensive judicial records.

Trump, who conducted interviews with seven candidates earlier this week for a spot on the top U.S. judicial body, told reporters aboard Air Force One en route to a rally in Montana that he would make a decision by Sunday and announce it at 9 p.m. EDT on Monday.

He said he had narrowed the search for a replacement for Justice Anthony Kennedy, who last week announced plans to retire after three decades on the high court, to four finalists, and was focusing primarily on just two or three.

Kennedy, a conservative who sometimes sided with the court’s liberals on divisive social issues such as gay rights and abortion, was a key figure on the court.

Conservative activists want Trump to replace him with a nominee who is more unwaveringly conservative. Trump’s appointee would maintain the slim 5-4 conservative majority on the court.

Kennedy’s retirement gives Trump a second opportunity to re-shape the court. Trump last year appointed conservative Justice Neil Gorsuch to take a seat that the Republican-led U.S. Senate, which must confirm nominees to the high court, had prevented Democratic former President Barack Obama from filling in 2016 following the death of conservative Justice Antonin Scalia.

Kethledge, 51, was appointed to his current post by Republican former President George W. Bush and was confirmed by the Senate in 2008.

In one notable case, he ruled in favor of a conservative Tea Party group that had sued the Internal Revenue Service over alleged mistreatment during the Obama administration. Prior to that, he spent most of his career in private practice.

Kavanaugh, 53, was picked by Bush to serve on the influential Washington-based appeals court in 2003. Contentious confirmation hearings in the Senate delayed his confirmation until 2006.

Prior to his appointment, Kavanaugh worked as a lawyer in the White House under Bush. Some conservatives activists have criticized Kavanaugh for his ties to the Bush family and some of his rulings, which they say indicate he would not be sufficiently conservative.

Both Kavanaugh and Kethledge have lengthy conservative judicial records.

Coney Barrett, 46, was a law professor at Notre Dame Law School in Indiana before Trump appointed her to her current position in October. She won Senate confirmation on a 55-43 vote.

During the confirmation process, Senate Democrats questioned Barrett about her Catholicism and past writings in which she said Catholic judges were in a “legal bind” in cases related to abortion and the death penalty.