A Congressional committee has voted to order key White House aides to testify under oath about the controversial firing of eight federal prosecutors.

The White House has offered to let the aides speak to Congress, but not under oath, and will resist the new order.

Congress wants to question Karl Rove, President Bush's top political adviser, as well as Mr Bush's former lawyer.

Lawmakers are probing the dismissal last year of eight US attorneys, which critics say was politically motivated.

Mr Bush's Attorney General, Alberto Gonzales, has faced calls to resign over the dismissals.

The president has thus far stood by Mr Gonzales, a long-time confidant from their days in Texas before they came to Washington together.

Private offer

Mr Gonzales says the prosecutors were dismissed because their performances were below standard.

Congressional investigations have found that Mr Bush's former counsel, Harriet Miers, proposed firing all 93 US attorneys nationwide in 2005.

One of the attorneys who was fired was replaced by a former aide to Mr Rove.

Mr Bush said on Tuesday that Congress should accept his offer to let his aides testify privately, without oath or transcript.

He vowed to resist any order, or subpoena, for them to testify in public.

"We will not go along with a partisan fishing expedition aimed at honorable public servants," Mr Bush said.

The BBC's Jonathan Beale in Washington says the House demand for testimony under oath sets up a constitutional battle between the president and Congress which could end up in the Supreme Court.

Democrats' anger

The criticism of Mr Gonzales began with the Democrats who now control Congress, but some Republicans have joined the chorus.

The Senate voted overwhelmingly - and with bipartisan support - on Tuesday to strip Mr Gonzales of the power to appoint US attorneys without its consent.

And the vote on Wednesday authorizing the use of subpoenas to compel White House officials to testify passed on a voice vote with no dissent.

Critics of the prosecutor firings - including some of the prosecutors themselves - say they were removed for investigating Republican officials or failing to investigate alleged vote fraud in support of Democrats.

Photo caption

President George Bush