Linda Tripp, the other woman on the Monica Lewinsky tapes, went before a grand jury Tuesday to tell what she knows about an alleged presidential affair and cover-up and to counter perceptions she manipulated the former White House intern.

Her appearance at the U.S. District Courthouse marks a critical juncture in the investigation, as prosecutor Kenneth Starr tries to press beyond proving a sexual relationship between Lewinsky and President Clinton to possible obstruction of justice and witness tampering.Tripp was accompanied by three lawyers and her children as she arrived at the courthouse. Asked if she was nervous, she replied only with a smile. Her lead attorney, Anthony Zaccagnini, said, "Not at all. She's doing good. She's real strong."

And with that, unaccompanied, Tripp entered the grand jury room for questioning that could stretch over several days.

A crowd of about 300 journalists struggled to get a view - or a question in - as she arrived at the federal building where dozens of grand jury witnesses have preceded her.

In an interview in Tuesday's Washington Post, Tripp said she had been vilified. "I am so anxious to go before the grand jury and tell the truth," she told the Post.

At the White House, presidential aides were withholding any criticism of Tripp while keeping a watchful eye on a witness whose account could undercut Clinton's denial of a sexual relationship with Lewinsky. "We'll let the American people draw their own conclusions about Linda Tripp," spokesman Jim Kennedy said.

Tripp in 1993 became executive assistant to Clinton's White House counsel, Bernard Nussbaum, and now works for the Pentagon. She precipitated a criminal probe of Clinton in January when she took 20 hours of secretly recorded telephone conversations with Lewinsky to prosecutors.

But in addition to her discussions with Lewinsky, Tripp had contact last year with presidential confidant Bruce Lindsey and presidential accuser Kathleen Willey at a time when the White House was scrambling to contain potential damage from the Paula Jones sexual harassment lawsuit against the president.

In the Post interview, Tripp dismissed allegations that she had betrayed Lewinsky and had cynically tried to use their friendship as Pentagon co-workers against Clinton. "I did not cultivate Monica - she cultivated me," Tripp told the Post. "Monica is a very worldly person. She educated me."