House Democrats on Tuesday asked a top Justice Department aide to come to Capitol Hill for a private interview in the next week on the firing of federal prosecutors. They said she cannot simply refuse to testify on the matter.

Monica Goodling, who has said she would assert her Fifth Amendment right against self-incrimination to avoid appearing at Senate hearings, must tell Congress which specific questions she's refusing to answer, Democrats said in a letter to her lawyer.

Goodling was senior counsel to embattled Attorney General Alberto Gonzales and was the department's White House liaison before she took a leave earlier this month amid the uproar over the ouster of eight U.S. attorneys.

With Gonzales' credibility about his role in question and the White House now pushing to get him to Capitol Hill quickly to testify about it, lawmakers say Goodling's account could be crucial to their probe of the firings.

After she was subpoenaed by the Senate Judiciary Committee, her lawyer John Dowd told lawmakers last week that Goodling would not appear. He called the congressional investigation a perjury trap for his client and said she could be in "legal jeopardy" even if she testified truthfully.

"Her claims do not constitute a valid basis for invoking the privilege against self-incrimination," Reps. John Conyers of Michigan and Linda Sanchez of California wrote in a letter to Dowd Tuesday.

Lawmakers' doubts about Gonzales' credibility and that of his deputy, Paul McNulty, do "not in any way excuse your client from answering questions honestly and to the best of her ability," wrote Conyers, the House Judiciary chairman, and Sanchez, who heads the subcommittee handling the inquiry.

"If her testimony is truthful, she will have nothing to worry about in terms of a perjury prosecution," the Democrats wrote.

Dowd said Tuesday that Goodling wouldn't change her stance, and he suggested the Democrats were trying to intimidate her into testifying.

"Threats of public humiliation for exercising her 5th and 6th Amendment rights are not well taken," Dowd said in an e-mail responding to the letter. "In a free country, every citizen should have the liberty to exercise their rights without threats or coercion."

There have been questions about whether Goodling and others misinformed McNulty about the firings just before he testified before the Senate committee in February.

Gonzales' truthfulness about the firings of seven prosecutors on Dec. 7 and another one months earlier is also in question.

He initially said he was never involved in discussions about the firings — a position he later changed to say he was minimally aware of plans to remove the prosecutors. Last week, his former chief of staff said Gonzales was regularly briefed and participated in talks about "this process of asking certain U.S. attorneys to resign."

Growing numbers of Democrats and Republicans are demanding that Gonzales to step down.

Bush, who is scrambling to recover from a personnel flap that has morphed into a full-blown scandal for his administration, said Tuesday that he regretted the uproar over prosecutors.

"I am genuinely concerned about their reputations, now that this has become a Washington, D.C., focus. I'm sorry it's come to this. On the other hand, there had been no credible evidence of any wrongdoing," the president said at a White House news conference.

Goodling was one of five senior Justice Department aides who met with Gonzales for a Nov. 27 discussion where he approved a detailed plan to carry out the dismissals. Department documents show she attended multiple meetings about the dismissals for months.

She also was among aides who on Feb. 5 helped McNulty prepare his testimony for a Senate hearing on the firings the next day.

Additionally, Goodling was involved in an April 6, 2006, phone call between the Justice Department and Sen. Pete Domenici, R-N.M., who had complained to the Bush administration and the president about David Iglesias, then the U.S. attorney in Albuquerque. Domenici wanted Iglesias to push more aggressively on a corruption probe against Democrats before the 2006 elections.