A US Senate committee has voted to authorise legal orders compelling key White House aides to testify over the sacking of eight US prosecutors.
George W Bush said he did not want confrontation with Democrats
The subpoenas target senior White House aides, including President George W Bush's political adviser Karl Rove.
The Democratic Party, in control of Congress, is pushing to expand an investigation into the sacking of the federal prosecutors last year.
A House committee has already approved subpoenas, but none has been issued.
President Bush has said he opposes any attempt to have White House aides testify under oath.
He has said he will allow the aides to testify in private, not under oath, and without transcripts.
Critics say the sacking of the eight attorneys was politically motivated but the Attorney General, Alberto Gonzales, has said their performance was below standard.
Mr Gonzales has faced calls to resign over the dismissals but the president has so far stood behind him - a long-time confidant from their days in Texas before they came to Washington together.
Mr Gonzales is fighting to hold onto his job
The chairman of the Senate Judiciary Affairs Committee, Patrick Leahy, said testimony under oath was essential to get to the bottom of the matter.
"Actually, if you're in public and under oath, you tend to get lot more accurate," he said.
But White House spokesman Tony Snow accused the Democrats of wanting to mount a public spectacle.
"I know a lot of people want this Showdown at the OK Corral king of thing," he said on ABC television.
"People might have a beef if we were withholding anything. We're not."
Subpoenas for the five White House aides have not been issued, but their approval means they could be used as a bargaining chip.
Serve at the discretion of the president, with the approval of the Senate
Prosecute criminal cases brought by the government
Prosecute or defend civil cases in which the government is a party
Collect debts owed to the government
Source: US Department of Justice
"It'll only strengthen our hand in getting to the bottom of this," said Democratic Senator Charles Schumer.
The top Republican on the Senate panel, Arlen Specter, counselled caution, saying: "We don't need a constitutional confrontation."
Mr Specter was working behind the scenes to avoid a court battle between the executive and the legislature, news agency AP reported.
There are 93 federal prosecutors in the US who investigate and prosecute court cases for the government.
They can be dismissed at any time but it is more usual for all 93 to be replaced when a president takes office.