Two senior Democrats who are spearheading the Senate’s investigation of eight controversial U.S. attorney firings on Friday urged the White House to reconsider its avowedly non-negotiable offer for private and non-transcribed interviews with senior White House aides tied to the scandal.

The Democrats' comments came as Kyle Sampson, who resigned as chief of staff to Attorney General Alberto Gonzales after the U.S. attorneys scandal broke, agreed to voluntarily testify before the Senate Judiciary Committee next Thursday. Sampson's lawyer had initially hesitated but complied to avert a threatened subpoena.

Sens. Charles Schumer (D-N.Y.) and Dianne Feinstein (D-Calif.) hailed a counter-offer floated on Thursday by Sen. Arlen Specter (Pa.), ranking Republican on Judiciary, as a way to open up the lines of communication with the administration. Yet the White House continues to stand firm on the deal that White House Counsel Fred Fielding offered lawmakers earlier this week.

“Sen. Specter’s proposal to the White House puts the onus on the White House to come back and negotiate with [Judiciary Chairman Patrick Leahy (Vt.) and other Democrats],” Schumer said. He described Specter’s offer as evidence that “you have the lead Republican and the lead Democrat a lot closer to each other than to the White House.”

Specter had suggested open testimony from the White House aides in question, including top political adviser Karl Rove, former presidential counsel Harriet Miers and their deputies. There would be a transcript but no oath, which the White House and lawmakers agree does not shield the aides from prosecution for making false statements to Congress.

“The defensive mode of the White House … is not really called for,” Feinstein said, adding later that President Bush’s administration has compromised its own credibility with Congress by not reaching out to legislators earlier in his term.

“I have no one to talk to who will tell me the truth,” she said.

In a later statement, Schumer praised Sampson for agreeing to share his story next week: "[His] testifying voluntarily is a major breakthrough since he appears to dispute [the Justice Department's] story about who knew what and when."