Bush has said he wants his pick confirmed and seated on the bench by the time the court convenes for its new term in October. Hearings are likely in late August or early September.

Roberts has won Senate confirmation once before — he was approved in 2003 when the president named him to his current post on the U.S. Court of Appeals for the District of Columbia Circuit.

His professional resume also includes a turn as clerk to William H. Rehnquist, who is 80 and battling thyroid cancer but recently affirmed his intention to remain as chief justice as long as his health allows.

Advocacy groups on the right say that Roberts, a native of Buffalo, N.Y., who graduated with honors from Harvard Law School in 1979, is a bright judge with strong conservative credentials he burnished in the administrations of former Presidents Bush and Reagan. While he has been a federal judge for just a little more than two years, legal experts say that whatever experience he lacks on the bench is offset by his many years arguing cases before the Supreme Court.

Liberal groups, however, say Roberts has taken positions in cases involving free speech and religious liberty that endanger those rights. Abortion rights groups allege that Roberts, while deputy solicitor general during former Bush's administration, was hostile to women's reproductive freedom and cite a brief he co-wrote in 1990 that suggested the Supreme Court overturn Roe v. Wade, the landmark 1973 high court decision that legalized abortion.

"The court's conclusion in Roe that there is a fundamental right to an abortion . . . finds no support in the text, structure or history of the Constitution," the brief said.

In his defense, Roberts told senators during his 2003 confirmation hearing that he would be guided by legal precedent. "Roe v. Wade is the settled law of the land. . . . There is nothing in my personal views that would prevent me from fully and faithfully applying that precedent."

While he doesn't have national name recognition, Roberts is a Washington insider who has worked over the years at the White House, Justice Department and in private practice.

In the Reagan administration, Roberts was special assistant to the attorney general and associate counsel to the president. Between 1989 and 1993, he was principal deputy solicitor general, the government's second-highest lawyer, who argues cases before the U.S. Supreme Court.