President Bush appears to be headed towards a constitutional showdown with the Democratic-controlled Congress over the firings of eight federal prosecutors. 

The U.S. House Judiciary Committee has voted to authorize subpoenas in an attempt to force senior White House officials to testify about their role in the controversial firings.

White House deputy chief of staff Karl Rove

On Tuesday, House and Senate Democrats rejected Mr. Bush's offer to allow congressional investigators to privately interview his chief political adviser Karl Rove and former counsel Harriet Miers.  Democratic leaders are calling for Rove and Miers to testify publicly, under oath, and for the record.

Critics of the firings say they were politically motivated, that senior White House officials were deeply involved, and that top Justice Department officials misled members of Congress about the reasons for the dismissals.

Mr. Bush says all federal prosecutors "serve at the pleasure of the president," and can be fired at any time.

Legal experts say it is unusual for U.S. attorneys to be fired in the middle of a president's term, instead of at the beginning.

President Bush says he is prepared to fight congressional leaders in court if they subpoena White House aides. 

Some lawmakers are calling on Attorney General Alberto Gonzales to resign over his handling of the firings.  The Senate voted overwhelmingly Tuesday to end the attorney general's ability to appoint U.S. attorneys without Senate confirmation.