WASHINGTON — Supreme Court nominee John Roberts earned a "well qualified" rating from the American Bar Association yesterday, clearing one hurdle in his path to joining the high court.

The rating by unanimous vote of an ABA committee was disclosed as the Senate Judiciary Committee announced plans for the start of confirmation hearings on Sept. 6. Roberts will face almost an hour of questioning from each of the 18 senators on the committee. The committee also will hold one hearing that will be closed to the public.

For more than 50 years, the ABA has evaluated the credentials of nominees for the federal bench, although the nation's largest lawyers' group has no official standing in the process. Supreme Court nominees get the most scrutiny.

The possible ratings are "well qualified," "qualified" and "not qualified."

"Judge Roberts is a mainstream nominee, and extremely well qualified, despite the efforts by some to mischaracterize him," said a Republican supporter on the Judiciary Committee, Sen. John Cornyn of Texas.

The top Democrat on the Senate committee said ABA reviewers were unable to look at all of Roberts' documents from his time as a government lawyer. Roberts worked in the Solicitor General's Office under the first President Bush and in the White House counsel's office under President Reagan.

"It's regrettable that they were not able to take the time to review the documents that now have been provided to the Senate," said Sen. Patrick Leahy of Vermont. "Nor have they or the Senate yet had access to work papers from Judge Roberts' most substantive earlier post, in the Solicitor General's Office."

One committee Democrat, Sen. Charles Schumer of New York, said yesterday that Roberts should explain why he kept hearing a lawsuit against the Bush administration while he was being interviewed for the Supreme Court.

Roberts sat on a three-judge panel that in July refused to block military tribunals for terrorism suspects. Bringing suit was Salim Ahmed Hamdan, a Yemeni who once was Osama bin Laden's driver.

Roberts had begun interviewing with administration officials in April for a possible vacancy on the Supreme Court, according to his questionnaire submitted to the Senate.

Three legal ethicists said in the online magazine Slate that Roberts should have recused himself from the case to avoid an "appearance of partiality."

If one side in a case "can secretly approach the judge about a dream job while the case is still under active consideration," trust in the judiciary suffers because it's not clear how the offer affected the judge's decision, wrote Stephen Gillers, David Luban and Steven Lubet.

White House spokeswoman Dana Perino dismissed the article. "There was no conflict whatsoever," she said.

The White House argues it would be impossible for D.C. Circuit judges hoping for advancement to step aside in every case affecting presidential priorities, because that court hears mostly federal cases.