The president has given national security officials 180 days to review the remaining documents.
"As long as the government is withholding documents like these, it's going to fuel suspicion that there is a smoking gun out there about the Kennedy assassination", said Patrick Maney, a presidential historian at Boston College.
A federal law required them all to be released on 26 October 2017, unless the President decided otherwise.
The British Security Service MI5 said the call was made to the senior reporter of the newspaper, the BBC reported.
Even as two clergymen hovered over the fallen president in the hospital emergency room, doctors and nurses administered blood transfusion.
The murky official conclusion regarding Kennedy's death - that he was killed by lone gunman Lee Harvey Oswald, has led to a variety of conspiracy theories surrounding the president's death.
JFK's widow Jackie reportedly had suspicions about her husband's successor, but this is the first time Johnson has been connected with the conspiracy in a government document. The phrase "no credible evidence to suggest" runs all through the Warren Report, giving commissioners room to be wrong.
■ How many files are there?
President Trump had confirmed on Saturday that he would allow for the opening of the documents, "subject to the receipt of further information".
Cambridge News told to call American Embassy in London for some 'big news' on November 22, 1963.
■ Why make it public now?
■ Will there be any bombshells? The CIA theory, popularized by director Oliver Stone's 1991 film JFK, has remained the most popular. The files that were withheld in full were those deemed "not believed relevant", Judge John Tunheim of Minnesota told AP.
Edgar Hoover it was 'inexcusable' that Lee Harvey Oswald was shot and killed before he could be interviewed.
Officials said on Thursday that they would not comment on conspiracy theories, including one propagated by Trump, about the father of a sitting senator.
As well, the House Select Committee on Assassinations concluded after a two-year inquiry in 1979 that Kennedy was "probably assassinated as the result of a conspiracy". President Kennedy was shot at 12.30 p.m. "The motorcade sped on".