The Justice Department refused Friday to turn over documents that Senate Democrats have demanded about Supreme Court nominee John G. Roberts Jr., escalating the most serious conflict in a confirmation process that has been more placid than either side had predicted.

The attorney general's office said in four-page letters to each of the eight Democrats on the Judiciary Committee that it was "simply contrary to the public interest" to release certain records from Roberts's service in the solicitor general's office, which argues cases before the Supreme Court on behalf of the executive branch.

"For the Solicitor General's office to perform its public service effectively, the internal deliberations of the office must remain confidential," the letter said.

It added that "the public interest in the office's zealous representation of the interests of the United States would be compromised by a breach of that confidentiality."

Democrats reacted angrily, accusing President Bush and his subordinates of "stonewalling" legitimate demands for information that would help them understand Roberts's legal philosophy. But they acknowledged they saw no immediate avenue of appeal, even as they vowed to find other ways to illuminate Roberts's tenure at the Justice Department from 1989 to 1993.

Roberts was principal deputy solicitor general under President George H.W. Bush and went before the justices to argue the government's position numerous times. Democrats had asked for memos and other documents related to 16 cases involving such sensitive issues as abortion, civil rights, environmental protection and freedom of speech.

Roberts has said his personal views cannot fairly be inferred from a position he argued on behalf of an administration. This prodded Democrats to seek documents that might have revealed his opinions about the positions he was taking in internal deliberations about the merits of different arguments, and whether the government should intervene.

Strategists in both parties predicted that Democrats now will try to make the documents a central issue in the Judiciary Committee's televised confirmation hearings for Roberts, which are scheduled to begin Sept. 6, the day after Labor Day.

Democratic Senate aides acknowledged that the Roberts record has given their party little ammunition. This leaves the fight for documents as a linchpin of the opposition strategy because it allows lawmakers to criticize the administration without attacking the judge personally.

Sen. Patrick J. Leahy (Vt.), the committee's top Democrat, said the rejection was part of an administration pattern of "stonewalling the Senate and the public," and asserted that his party's request had been "a carefully crafted and narrow request for a few documents that might illuminate Judge Roberts's views on important issues of concern to all Americans -- civil rights, privacy and access to justice."

In what the administration called an effort to partly comply with the Democrats' request, officials Friday night released a stack of records several feet high. But the release almost entirely consisted of legal briefs that are already readily available in libraries and on-line databases.

The White House defended the pace and quantity of the release of documents, saying Friday in a letter to Sen. Charles E. Schumer (D-N.Y.) that the administration was providing 65,000 pages of documents to the committee, including certain records from Roberts's days in the White House counsel's office under President Ronald Reagan.