Veterans Affairs Secretary Anthony Principi (search) announced Wednesday that he is resigning. He distributed a resignation letter to staff at his department.

Principi, who has been in the Bush administration since its inception, said he wants to move on to new responsibilities and challenges.

"I am humbled to have worked side-by-side with you, the men and women who bring VA to life, as you demonstrated every day an all encompassing commitment to our mission and documented your skills in the changed lives of the veterans we serve. Our mission is profoundly satisfying, and you earned your place in the first rank of competence and compassion," Principi wrote in a three-paragraph letter.

Principi is the ninth of President Bush's Cabinet members to leave his post. He is a graduate of the U.S. Naval Academy and a decorated Vietnam veteran.

Also on Wednesday, the White House announced that Treasury Secretary John Snow (search) is staying in his post.

In a written statement, Bush thanked Principi for his service.

"Under Tony's leadership, we have honored our veterans for their service and sacrifice by increasing and improving health care services, working to eliminate the waiting list for medical care and cutting the disability claims backlog. I appreciate his efforts to improve access to health care for low-income veterans and those with service-related disabilities ... I thank Tony for serving our veterans and our country with integrity and dignity," Bush said.

The changeover in Bush's Cabinet is on the high side for a second-term president. Presidents Clinton and Reagan saw seven Cabinet seats change hands after they won new terms, President Nixon nine and Presidents Truman and Johnson four each.