The Bush administration is rebuffing requests from members of the Senate Judiciary Committee for its classified legal opinions on President Bush's domestic spying program, setting up a confrontation in advance of a hearing scheduled for next week, administration and Congressional officials said Wednesday.

Mr. Specter said that he wanted a fuller explanation as to how the Justice Department asserts that the eavesdropping operation does not conflict with the 1978 Foreign Intelligence Surveillance Act, which set strict and "exclusive" guidelines for intelligence wiretaps.

The operation was approved by President Bush, to allow the National Security Agency to conduct wiretaps on Americans' international communications without a court warrant. Mr. Specter said his view was that the operation "violates FISA — there's no doubt about that."

He also questioned why the administration did not go to Congress or the intelligence court to seek changes in the process before moving ahead on its own with the classified program after the Sept. 11 attacks.