Visitors line under a poster of former U.S. President John F. Kennedy to enter the Newseum in Washington D.C., the United States, on Oct. 26, 2017. (Xinhua/Yin Bogu)

WASHINGTON, Oct. 26 (Xinhua) -- U.S. President Donald Trump decided on Thursday not to release all of more than 3,000 unseen files related to former President John F. Kennedy's assassination, citing national security concerns.

The U.S. National Archives on Thursday night released more than 2,800 previously classified records on the assassination over half a century ago, so as to comply with a 1992 law, with about 300 files are still pending review.

In a memo signed earlier on the day, Trump said he "has no choice" but to keep some files secret as requested by some government agencies.

Meanwhile, the president directed agencies that requested redactions to re-review their reasons for withholding these information within six months.

"The American public expects and deserves its government to produce as much access as possible to the John F. Kennedy assassination records," Trump wrote.

The Central Intelligence Agency (CIA) said the redactions were meant to protect information that would "harm national security - including the names of CIA assets and current and former CIA officers, as well as specific intelligence methods and partnerships that remain viable to protecting the nation today."

"Every single one of the approximately 18,000 remaining CIA records in the collection will ultimately be released, with no document withheld in full," the agency said in a statement.

Most of the files are believed to be from the 1960s and 1970s, stemming from the 1963 assassination and aftermath.

But several dozens were generated by government agencies in the 1990s in apparent response to the conspiracy theories stirred by the controversial Oliver Stone film "JFK."

The U.S. Congress passed the Kennedy Assassination Records Collection Act in 1992, requiring that the millions of pages, many of them contained in CIA and the Federal Bureau of Investigation, be published in 25 years.

Over the years, the National Archives has released most of the documents, either in full or partially redacted.

But one final batch remains, and only the U.S. president has the authority to extend the papers' secrecy past the deadline on Thursday.

Kennedy, the 35th U.S. president, was shot dead on Nov. 22, 1963 in Dallas, Texas. Lee Harvey Oswald, who was alone accused of the shooting, was killed two days later by Jack Ruby.