"We are cooperating fully with the review, which I hope will be finished soon," Biden said.

Biden's attorneys discovered fewer than a dozen classified records inside the office at the think tank and informed the U.S. National Archives of their discovery, turned over the materials, and said they were cooperating with the Archives and the Justice Department.

Biden defended the handling of the documents.

"They found some documents in a box in a locked cabinet, or at least a closet. And as soon as they did, they realized there were several classified documents in that box. And they did what they should have done. They immediately called the Archives," he said.

"I was briefed about this discovery and surprised to learn that there were any government records that were taken there to that office, but I don't know what's in the documents," he said.

He said his lawyers have suggested he not ask what was in the documents.

"I've turned over the boxes, they've turned over the boxes to the Archives, and we are cooperating fully with the review, which I hope will be finished soon. And there'll be more detail at that time," he said.