In this Nov. 23, 1963 file, surrounded by detectives, Lee Harvey Oswald talks to the media as he is led down a corridor of the Dallas police station for another round of questioning in connection with the assassination of US President John F. Kennedy. (Photo:IC)

Senior administration officials say the CIA and the FBI made most of the requests to continue to withhold information from the release of the last trove of secret files about the assassination of President John F. Kennedy.

The collection includes more than 3,100 documents — comprising hundreds of thousands of pages — that have never been seen by the public. About 30,000 documents were released previously — with redactions. The National Archives is to release 2,800 of the remaining records now.

President Donald Trump has asked all agencies, including the CIA and FBI, to go back and review their suggested redactions so that even more of the material can be released in coming months.

A 1992 law required all government records related to the assassination to be "publicly disclosed in full" within 25 years. The deadline was Thursday.