U.S. Sen. Mitch McConnell, R-Ky., says he will oppose Judge Sonia Sotomayor's bid to join the Supreme Court, even as other GOP lawmakers have endorsed her.

In prepared remarks to be delivered to Congress Monday, McConnell says Sotomayor has displayed an "alarming" willingness to treat people unequally under the law, CNN reported.

"Judge Sotomayor's record of written statements suggest an alarming lack of respect for the notion of equal justice, and, therefore, in my view, an insufficient willingness to abide by the judicial oath," McConnell said. "This is particularly important when considering someone for the Supreme Court since, if she were confirmed, there would be no higher court to deter or prevent her from injecting into the law the various disconcerting principles that recur throughout her public statements."

McConnell's move to oppose President Barack Obama's high court nominee came after three key Republican senators, Richard Lugar of Indiana, Mel Martinez of Florida and Olympia Snowe of Maine, said they would vote for Sotomayor's nomination, all but assuring her confirmation by the Senate, the broadcaster reported.

Lugar was the first Republican to say he would vote in favor of Sotomayor's nomination to the nation's highest court.