Trove of JFK assassination records released by National Archives

More records related to President John F. Kennedy's assassination were released Thursday by the National Archives.

The agency released 13,173 documents containing new information, stating now over 97% of records in the collection are publicly available. Originally, the National Archives said 12,879 documents were being released but later updated the total due to "last minute additions."

President Joe Biden authorized the release of the documents, but will continue to block some materials from public view until June 30, 2023, claiming releasing them now would result in "identifiable harm."

"I agree that continued postponement of public disclosure of such information is warranted to protect against an identifiable harm to the military defense, intelligence operations, law enforcement, or the conduct of foreign relations that is of such gravity that it outweighs the public interest in disclosure," Biden said in a memorandum released Thursday afternoon.

Biden stated that after a "comprehensive effort" to review a full set of 16,000 records that were previously released in redacted form, more than 70% of those records would now be released in full.

Kennedy was shot and killed in November 1963 during a visit to Dallas, Texas, at the hands of Lee Harvey Oswald.

Last year, the National Archives released roughly 1,500 documents related to Kennedy's killing. Among the documents made public last year were CIA memos discussing Oswald's trips to the Soviet and Cuban embassies in Mexico City in the months before the assassination.

The 1992 John F. Kennedy Assassination Records Collection Act dictated all assassination records to be publicly disclosed within 25 years, or by 2017, but postponements have been made in instances of national security concern.

"President Biden believes all information related to President Kennedy's assassination should be released to the greatest extent possible, consistent with again, national security," White House press secretary Karine Jean-Pierre told reporters during Thursday's briefing. "That's why he directed the acting archivist to conduct a supplementary six-month review of a subset of the remaining redacted records to ensure they are disclosed to the greatest extent possible."

The CIA released a statement Thursday in which it explained why it wanted some records withheld, citing the need to protect intelligence sources.

"What little information remains redacted in CIA records in the Collection consists of intelligence sources and methods -- some from as late as the 1990s, provided initially to give the JFK Review Board overall context on the CIA -- the release of which would currently do identifiable harm to intelligence operations……CIA believes all of its information known to be directly related to the assassination of President John F. Kennedy in 1963 has already been released. Likewise, we are not aware of any documents known to be directly related to Oswald that have not already been made part of the Collection."

The CIA said that overall 95% of the agency's documents within the Kennedy records collection have been released in their entirety, and "no documents remain redacted or withheld in full."

ABC News' Cindy Smith contributed to this report.