Washington ? President Clinton’s national security adviser, Sandy Berger, is the focus of a Justice Department investigation after removing highly classified terrorism documents and handwritten notes from a secure reading room during preparations for the Sept. 11 commission hearings.

Berger’s home and office were searched earlier this year by FBI agents armed with warrants after he voluntarily returned documents to the National Archives. However, still missing are some drafts of a sensitive after-action report on the Clinton administration’s handling of al-Qaida terror threats during the December 1999 millennium celebration.

Berger and his lawyer said Monday night he knowingly removed handwritten notes he had made while reading classified anti-terror documents at the archives by sticking them in his jacket and pants. He also inadvertently took copies of actual classified documents in a leather portfolio, they said.

“I deeply regret the sloppiness involved, but I had no intention of withholding documents from the commission, and to the contrary, to my knowledge, every document requested by the commission from the Clinton administration was produced,” Berger said in a statement.

Lanny Breuer, one of Berger’s attorneys, said his client has offered to cooperate fully with the investigation but had not yet been interviewed by the FBI or prosecutors. Berger has been told he is the subject of the criminal investigation, Breuer said.

Berger served as Clinton’s national security adviser for all of the president’s second term and most recently has been informally advising Democratic presidential candidate John Kerry.

Some files lost

The FBI searches of Berger’s home and office occurred after National Archives employees told agents they believed they saw Berger place documents in his clothing while reading sensitive Clinton administration papers and that some documents were then noticed missing, officials said.

When asked, Berger said he returned some classified documents that he found in his office and all of the handwritten notes he had taken from the secure room, but could not locate two or three copies of the highly classified millennium terror report.

“In the course of reviewing over several days thousands of pages of documents on behalf of the Clinton administration in connection with requests by the Sept. 11 commission, I inadvertently took a few documents from the Archives,” Berger said.

“When I was informed by the Archives that there were documents missing, I immediately returned everything I had except for a few documents that I apparently had accidentally discarded,” he said.

Breuer said Berger believed he was looking at copies of the classified documents, not originals.

Berger was allowed to take handwritten notes but also knew that taking his own notes out of the secure reading room was a “technical violation of Archive procedures, but it is not all clear to us this represents a violation of the law,” Breuer said.

Government and congressional officials familiar with the investigation, who spoke only on condition of anonymity because the probe involves classified materials, said the investigation remained active and no decision had been made on whether Berger should face criminal charges.

Millennium threats

The officials said the missing documents were highly classified, and included critical assessments about the Clinton administration’s handling of the millennium terror threats as well as identification of America’s terror vulnerabilities at airports and sea ports.

Berger testified at one of the commission’s public hearings about the Clinton administration’s approach to fighting terrorism. The former president answered the panel’s questions at a private meeting.

Berger testified that during the millennium period, “we thwarted threats and I do believe it was important to bring the principals together on a frequent basis” to consider terror threats more regularly.

The missing documents involve two or three draft versions of the report as it was evolving and being refined by the Clinton administration, officials and lawyers say. The Archives is believed to have copies of some of the missing documents.