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

Sotomayor, poised to become the first Hispanic justice on the top US 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 in a vote expected by early August in the Democratic-controlled Senate and take her seat when the nine-member court hears its next case in September.

"She will be on the Supreme Court when they come in," Leahy 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.

Ss 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, opening the day's questions.

One of the chief plaintiffs in that case, Frank Ricci, was expected to testify as a witness later, a moment of drama in the proceedings.

"Mr. Ricci has a story to tell too, there are all kinds of stories to tell in this country," Republican Senator Lindsey Graham told Sotomayor.