A White House national security adviser under President Clinton, Samuel Berger, will plead guilty to a misdemeanor charge of mishandling classified information, the Justice Department announced yesterday.

Mr. Berger, 59, is scheduled to offer the plea at Washington this afternoon before a federal magistrate.

The charge stems from a period in 2003 when Mr. Berger was helping Mr. Clinton prepare for testimony before a national commission investigating the September 11, 2001 terrorist attacks.

A two-page criminal information prosecutors filed in federal court yesterday alleges that on two occasions Mr. Berger “knowingly removed” classified documents from the National Archives and stored the records in unauthorized locations, including at his consulting firm at the capital. The information, which is usually the product of negotiations between the government and a suspect’s attorneys, provided no detail about precisely which documents the former White House official allegedly mishandled.

A lawyer for Mr. Berger, Lanny Breuer, issued a brief statement last night in which his client expressed relief that the one-and-a-half-year-long investigation may soon be over.

“Mr. Berger has cooperated fully with the Department of Justice and is pleased that a resolution appears very near. We will have further comment tomorrow,” Mr. Breuer wrote.

The offense to which Mr. Berger is expected to plead guilty is punishable by a fine and a prison term of up to a year. Attorneys said it is highly unlikely that Mr. Berger, a first-time offender, will get any prison time.

A former international trade lawyer, Mr. Berger served in the White House throughout Mr. Clinton’s presidency. Mr. Berger was the deputy national security adviser during Mr. Clinton’s first term in office and took the lead national security job during the second term.

When word of the investigation into Mr. Berger’s conduct became public in July, he stepped down as a top foreign policy adviser to the Democratic presidential candidate, Senator Kerry of Massachusetts. Some Democrats blasted the disclosure as a politically motivated leak. Mr. Clinton later indicated that he had known about the inquiry for months.

At the time, Mr. Berger issued a statement saying, “In the course of reviewing over several days thousands of pages of documents … I inadvertently took a few documents from the archives.” Based on the wording of the charges filed yesterday, he now appears to have conceded that he took the documents deliberately.

“Presumably that admission of intent was necessary to close the matter,” a leading authority on classification issues, Steven Aftergood, said. “If he had declined to make that admission, then it would have remained an open investigation and possibly with even more serious consequences,” said Mr. Aftergood, who works for the Federation of American Scientists.

Federal prosecutors have great discretion when prosecuting breaches of classified information. Some breaches are punished informally or with administrative sanctions. Others can be treated as misdemeanors or felonies. In Mr. Berger’s case, there were somewhat fewer administrative options because he is no longer a government employee.

Bruce Fein, a former Justice Department official under President Reagan, said the criminal charge against Mr. Berger will boost pressure on prosecutors to indict a Bush administration official in connection with the leak of the identity of a CIA officer, Valerie Plame.

“It was monstrous compared to the triviality of Berger,” Mr. Fein said. He said the prosecutor probing the Plame leak, Patrick Fitzgerald, will now be “pushed all the harder to come up with an indictment.”

Mr. Fein said he suspected that politics were behind Mr. Berger’s decision to plead to a misdemeanor rather than fight a possible felony charge over the allegedly mishandled documents.

“It’s not the greatest thing in the world when you’re in the high altitude of Washington consulting to have a misdemeanor conviction. You don’t put it on your marquee. That’s why I’m suspicious,” Mr. Fein said. “If it went to trial, it may have some embarrassment to Clinton. He just didn’t want to get President Clinton involved.”

The inquiry into Mr. Berger’s action began after National Archives employees grew suspicious that he was removing some of the classified documents he was reviewing. On Mr. Berger’s next visit, the archivists reportedly set up a sting of sorts by marking documents in order to know exactly what was removed. The archives staffers concluded some documents were missing and reported the matter to the FBI, which carried out search warrants at Mr. Berger’s home and office. The results of the search warrants have never been made public.

Some of the documents Mr. Berger reportedly removed included an after-action report on the so-called Millennium plot to blow up American landmarks. In the report, Richard Clarke, a former counterterrorism adviser, fretted that the success in disrupting the plot was largely due to luck.

Archives officials initially said they were concerned that some the only copies of some memoranda might have been destroyed after Mr. Berger removed and apparently lost them. However, a spokeswoman for the archives later said staffers had located originals or copies of all the documents Mr. Berger reviewed.

Mr. Berger’s attorney, Mr. Breuer, angrily denied reports that Mr. Berger stuffed some documents in his socks.

A CIA director under Mr. Clinton, John Deutch, faced a similar charge in connection with allegations that he prepared and downloaded classified documents on his home computer. In 2001, Mr. Deutch also agreed to plead guilty to a misdemeanor, but he won a pardon from Mr. Clinton hours before the president left office.

Mr. Aftergood said the Justice Department lawyers probably chose to make an example of Mr. Berger because of his former high rank in the government. Still, the classification analyst said it is hard to excuse the conduct Mr. Berger has apparently agreed to admit.

“Berger signed off on it. Who can say that it was unwarranted?” Mr. Aftergood said. “I think the leak last year was unseemly and unprofessional, but I don’t think you can say the same thing about the conclusion.”