A former aide to US Attorney General Alberto Gonzales has contradicted his claim he was not involved in the sacking of eight federal prosecutors.
Kyle Sampson's testimony may increase pressure on Mr Gonzales
Kyle Sampson, who resigned over the affair, told a US Senate Judiciary Committee hearing he had discussed the process with Mr Gonzales.
He defended the dismissals as "properly made, but poorly explained". Critics say they were politically motivated.
Mr Gonzales, who faces calls to resign, may come before the committee in April.
Committee members voted last week to authorise legal orders compelling key White House aides to appear before them. No subpoenas have yet been issued.
The Democratic Party, in control of Congress, is pushing to expand an investigation into the sacking of the federal prosecutors last year.
Critics say the sacking of the eight attorneys was politically motivated but Mr Gonzales has said their performance was below standard.
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
He told reporters earlier this month that the sackings were an "effort that was led by Mr Sampson" and that they "never had a discussion about where things stood".
Testifying before the Senate Judiciary Affairs Committee on Thursday, Mr Sampson said: "I don't think that the attorney general's statement that he was not involved in any discussions of US attorneys' removals was accurate.
"I remember discussing with him this process of asking certain US attorneys to resign."
Mr Sampson said he believed Mr Gonzales had been present at a meeting in November at which the issue was discussed.
He also told the committee that the attorney general and the counsel to the president had been the "decision makers in this case", acting on recommendations he and others made.
Alberto Gonzales has come under pressure to resign
But he rejected suggestions that the dismissals had been improperly based on political bias, saying it was legitimate to judge politically-appointed attorneys on their support for the administration.
"The distinction between 'political' and performance-related' reasons for removing a United States attorney is, in my view, largely artificial," he added.
Mr Sampson denied seeking to conceal information but apologised for the fact that his efforts to explain the dismissals process had created "an ugly, undignified spectacle".
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.
Mr Bush has so far stood behind Mr Gonzales - a long-time confidant from their days in Texas before they came to Washington together.
The president has also 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.