WASHINGTON - Supreme Court nominee Sonia Sotomayor is defending her membership in an elite all-women's club, telling senators the group does not discriminate unfairly by gender and involves men in many of its activities.

Her explanation came in a letter Monday evening to the Senate Judiciary Committee and included copies of several rulings, briefs, and speeches the judge had not previously given the panel.

GOP senators had requested the material and questioned Sotomayor's membership in the Belizean Grove, a group of prominent professional women, because federal judges are bound by a code that says they should not join any organization that discriminates by race, sex, religion, or nationality.

"I do not believe that my membership in the Belizean Grove violates the Code of Judicial Conduct," Sotomayor wrote. She told senators that the group involved men in some of its events and that no man she knew of had ever tried to become a member.

Sotomayor's backers noted that the court's only current female justice, Ruth Bader Ginsburg, belongs to the membership-only International Women's Forum, as did former Justice Sandra Day O'Connor, who defended her involvement in all-women's groups during her Senate confirmation hearings.

Even as Republicans delved into Sotomayor's background, a key GOP senator was planning a series of speeches that will criticize Obama and Democrats for their approach to choosing judges, arguing that their approach threatens the court system and the rule of law.

Sen. Jeff Sessions of Alabama, the top Judiciary Committee Republican, was expected to begin making that case this week, with a speech about what the founding fathers considered an ideal justice. He planned to contrast that vision with a growing movement that he says wants judges to be able to impose their politics and personal feelings through their rulings and change the meaning of the Constitution.

Sessions' planned speeches - which do not include any direct criticism of Sotomayor or her record - came to light as Republicans struggle to figure out how to handle the politically charged debate over confirming the woman who would be the first Hispanic on the high court. GOP senators have neither the votes nor the appetite to try to block the judge, and seem loath to criticize her too strongly, for fear they will be tied to prominent conservatives outside the Senate who have called her racist.

The risk is particularly acute for Sessions, who was rejected for a spot on the federal bench more than 20 years ago after allegations surfaced that he made racist remarks and targeted black civil rights leaders as a prosecutor; Sessions denied the allegations, calling them the product of "very aggressive outside groups."