Bush: Congress can question aides - but not in public

US President George Bush and congressional Democrats could face a constitutional showdown over whether top White House aides will testify under oath about the firing of federal prosecutors.

“It will be regrettable if they choose to head down the partisan road of issuing subpoenas and demanding show trials,” Bush said, warning Democrats to accept his offer to allow political director Karl Rove and other top aides to speak to Congress – but not on the record, under oath or in public.