Historians and open-government advocates are concerned that Vice President Dick Cheney, who has long bristled at requirements to disclose his records, will destroy or withhold key documents that illustrate his role in forming U.S. policy for the last 7 1/2 years.

In a preemptive move, several of them have agreed to join the advocacy group Citizens for Responsibility and Ethics in Washington in asking a federal judge to declare that Cheney's records are covered by the Presidential Records Act of 1978 and cannot be destroyed, taken or withheld without proper review.

The group expects to file the lawsuit today in the U.S. District Court for the District of Columbia. It will name Cheney, the executive offices of the president and vice president, and the National Archives and chief archivist Allen Weinstein as defendants.

The goal, they say, is to protect a trove of information about national security, the wars in Iraq and Afghanistan, domestic wiretapping, energy policy and other major issues that could be hidden from the public if Cheney adheres to his view that he is not part of the executive branch and is not required to make his papers public after leaving office.

Access to the documents is crucial because he is widely considered to be the most influential vice president in U.S. history, they say.