Washington - President Barack Obama's Supreme Court pick Sonia Sotomayor appeared headed for confirmation as Senate hearings wound up on Thursday, but critics planned one last showdown over a controversial race ruling.

    Sotomayor, poised to become the first Hispanic justice on the top U.S. court, appeared for a fourth day before the Senate Judiciary Committee where she has coolly parried Republican attempts to depict her as unfit for the lifetime job.

    The committee's Democratic chairman Senator Patrick Leahy said there was little doubt she would be approved by the full Democratic-controlled Senate and take her seat when the nine-member court hears its next case in September.

    And the ranking Republican on the committee, Senator Jeff Sessions, said Republicans would not seek to block the confirmation vote, expected in the next several weeks.

    "I look forward to you getting that vote before we recess in August," Sessions said.

    Critics have focused on the 55-year-old appeals court judge's attitudes toward race, with Republicans hammering at Sotomayor for comments in which she said a "wise Latina' might be a better judge than a white man.

    On Thursday, as the issue came up again, she said she was sorry for the controversy. "I regret that I have offended some of you ... I believe my life demonstrates that that was not my intent."

    Sotomayor has also come under fire for upholding a lower court ruling which permitted the city of New Haven, Connecticut to junk firefighter exam results which did not produce enough qualified minority candidates.

    White firefighters who scored well on the test complained they were being discriminated against, and the Supreme Court later overturned Sotomayor's ruling, saying it could open the door to new types of racial quota systems.

    "It's an important decision and it can have far reaching implications," Republican Senator John Kyl said on Thursday, opening the final round of questions.

    One of the chief plaintiffs in that case, Frank Ricci, was expected to testify as a witness later on Thursday, a moment of drama in the proceedings which could stretch into Friday.

    "Good Chance" at the Job

    Sotomayor has followed precedent by deflecting questions about her position on divisive issues, including abortion, gun rights and gay marriage, saying it was not appropriate to comment as these might come before her on the court.

    Despite the grilling, Democrats and Republicans say it is almost certain that Sotomayor will be confirmed on the court, where she will replace retired Justice David Souter as one of four liberals facing five conservative justices.

    Leahy introduced for the record a letter of support from former President Bill Clinton, who hailed the "unique" contributions of a woman he had appointed to the appellate bench in 1998.

    Republican Senator Charles Grassley said the sparring over Sotomayor's appointment, which divided along partisan lines despite Obama's hopes of building bipartisan bridges, was a sign of battles to come over the judicial branch of the U.S. government.

    "Republicans on one side, Democrats on the other, seem to be asking different questions," Grassley said. "In the last 10 years, there's been a change in the environment here that is influencing that."

    Democrats were hopeful that Sotomayor's long legal resume and competent performance in the hearings had persuaded a number of Republicans to back her.

    "I think she will get a substantial number of Republican votes," said Senator Richard Durbin, the second-ranking Democrat in the Senate responsible for maintaining the party's vote tallies.

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    (Additional reporting by Richard Cowan; editing by David Storey)