Now, Mr. Trump has accepted a recommendation from the National Archives to keep the lid closed on some records for now, more than five decades after the 35th president was killed.

Mr. Trump wrote in a memo issued Thursday that some of the classified documents are "of such gravity that it outweighs the public interest in immediate disclosure." Mr. Trump allowed the release of some documents, but others, the president decided, will be delayed until 2021. The FBI and CIA had said the release could jeopardize national security.

The president ordered agencies to review the remaining documents in the next three years to determine which should be released.