The White House won't release documents on domestic surveillance or allow aides to testify on US attorney firings.
A flurry of subpoenas is pushing Congress and President Bush toward a historic clash over executive powers that could wind up in the courts.
For now, lawmakers are targeting two issues: the dismissal of nine US attorneys and the Bush administration's authorization of warrantless domestic surveillance.
If the president does not comply with these subpoenas Senate Judiciary Chairman Patrick Leahy said he will seek to cite the White House for criminal contempt of Congress. But the outcomes of these disputes also could tip the balance of powers between Congress and the executive branch for a generation.
"It feels like a climactic moment," says Julian Zelizer, a congressional historian at Princeton University. "The Bush administration has been about presidential power since they took office – even before 9/11."
"We've seen a push by Vice President Cheney to reverse everything that happened in the 1970s and fully restore the powers of the presidency. Now, Congress is responding to what he has done," he adds.
At issue is whether lawmakers have a right to question, under oath, two senior White House aides on the attorney firings, which critics say were motivated for improper political reasons or to squelch ongoing corruption investigations.
In a new batch of subpoenas last week, lawmakers are also seeking more information on the legal justification for the Bush administration's warrantless domestic surveillance program.
On Thursday, the White House invoked executive privilege in refusing to allow the release of documents requested by the Senate and House Judiciary Committees. If subpoenas for two former aides to testify are not withdrawn by the response date of July 12, Mr. Bush will also cite executive privilege in not permitting them to appear, said a senior administration official in a briefing last week.
"For the president to perform his constitutional duties, it is imperative that he receive candid and unfettered advice," said White House counsel Fred Fielding, in a letter to the Senate and House Judiciary committees last week.