President Bush invoked executive privilege Monday to deny requests by Congress for testimony from two former aides about the firings of federal prosecutors.

The White House, however, did offer again to make former counsel Harriet Miers and one-time political director Sara Taylor available for private, off-the-record interviews.

In a letter to the heads of the House and Senate Judiciary panels, White House counsel Fred Fielding insisted that Bush was acting in good faith and refused lawmakers’ demand that the president explain the basis for invoking the privilege.