WASHINGTON -- Archivist of the United States John Carlin was pressured by the White House in December to submit his resignation without being given any reason, Senate Democrats disclosed last week at a hearing to consider President Bush's nomination of his successor.

Democrats said the White House should explain why it asked Carlin to resign. In a letter to Sen. Carl Levin, D-Mich., Carlin said White House Counsel Alberto Gonzales called Dec. 5 and told him "the administration would like to appoint a new archivist. I asked why, and there was no reason given."

Critics have suggested that Bush may have wanted a new archivist to help keep his or his father's sensitive presidential records under wraps. Under the Presidential Records Act of 1978, many of President George H.W. Bush's papers are due to become public in January.

The 1984 law establishing the National Archives and Records Administration provides that the archivist will serve an indefinite term and can be replaced if he resigns or is removed by the president. If he is removed, "the president shall communicate the reasons for any such removal" to Congress, the law says.

Disclosure of the circumstances surrounding Carlin's decision to step down overshadowed testimony by Bush's nominee, Allen Weinstein, and could delay any plans to confirm him before the fall elections.

Carlin said in his July 22 letter to Levin that he would like to remain in his post for four more months, so he could complete several initiatives he had undertaken. They include getting congressional funding for development of "a groundbreaking system that will allow the government to manage and preserve any kind of electronic records, now and in the future."

Two weeks after the call from Gonzales, Carlin told the president that he would resign; his Dec. 19 letter contained no hint of what prompted his decision. Senate Governmental Affairs Committee Democrats said it amounted to a forced removal, and Bush should be required to give his reasons for it.

Committee Chairwoman Susan Collins, R-Maine, pointed out that Carlin has not quit yet. Appointed in 1995 by then-President Bill Clinton, Carlin wrote Bush that he would submit his formal resignation "upon the confirmation and swearing in" of the next archivist.

The White House would not say why Bush wanted to replace Carlin. Spokeswoman Erin Healey said: "Mr. Carlin has submitted a letter stating his intention to resign, and Mr. Bush has a responsibility to appoint someone to fill that position."

Weinstein, a historian and an expert on emerging democracies, won praise from both Republicans and Democrats for testimony about his determination to open as many government records as possible and his disdain for partisan considerations.