Washington ? President Bush, in a constitutional showdown with Congress, claimed executive privilege Thursday and rejected demands for White House documents and testimony about the firing of U.S. attorneys.

His decision was denounced as “Nixonian stonewalling” by the chairman of the Senate Judiciary Committee.

Bush rejected subpoenas for documents from former presidential counsel Harriet Miers and former political director Sara Taylor. The White House made clear neither one would testify next month, as directed by the subpoenas.

Presidential counsel Fred Fielding said Bush had made a reasonable attempt at compromise but Congress forced the confrontation by issuing subpoenas. “With respect, it is with much regret that we are forced down this unfortunate path which we sought to avoid by finding grounds for mutual accommodation.”

The assertion of executive privilege was the latest turn in increasingly hostile standoffs between the administration and the Democratic-controlled Congress over the Iraq war, executive power, the war on terror and Vice President Dick Cheney’s authority. A day earlier, the Senate Judiciary Committee delivered subpoenas to the offices of Bush, Cheney, the national security adviser and the Justice Department about the administration’s warrantless wiretapping program.

While weakened by the Iraq war and poor approval ratings in the polls, Bush has been adamant not to cede ground to Congress.

“Increasingly, the president and vice president feel they are above the law,” said Sen. Patrick Leahy, D-Vt., chairman of the Senate Judiciary Committee.

White House press secretary Tony Snow weighed in with unusually sharp criticism of Congress. He accused Democrats of trying “to make life difficult for the White House. It also may explain why this is the least popular Congress in decades, because you do have what appears to be a strategy of destruction, rather than cooperation.”