In that letter, published in The Times today under the headline "Judith Miller's Farewell," Ms. Miller said she was leaving partly because some of her colleagues disagreed with her decision to testify in the C.I.A. leak case. "But mainly," she wrote, "I have chosen to resign because over the last few months, I have become the news, something a New York Times reporter never wants to be."

Kenneth A. Richieri, The Times lawyer who negotiated the severance agreement for the paper, said one thing was clear to both sides from the start of those talks. "What made the deal possible was that shared understanding that she couldn't continue to report on national security matters for The New York Times," he said. "She'd become so much a part of the story."

Catherine Mathis, a spokeswoman for the paper, said it had been made clear to Ms. Miller that she would not be able to continue as a reporter of any kind, not just one covering national security.

Ms. Miller's reporting came under attack after articles suggested that Iraq possessed weapons of mass destruction, coverage that helped the Bush administration build its case for invading Iraq but that turned out to be wrong.

In her letter to the editor, Ms. Miller noted that even before going to jail, she had "become a lightning rod for public fury over the intelligence failures that helped lead our country to war." She said she regretted "that I was not permitted to pursue answers" to questions about those intelligence failures.

As part of the settlement, Mr. Keller made public a personal letter he wrote to Ms. Miller clarifying some elements of a memorandum he sent to the staff on Oct. 21 that she considered critical of her.

In his letter, Mr. Keller said he had never intended to imply she had an improper relationship with I. Lewis Libby Jr., her source and the former chief of staff for Vice President Dick Cheney, when he described their contact as an "entanglement."