"Subject to the receipt of further information, I will be allowing, as President, the long blocked and classified JFK FILES to be opened," Trump tweeted.
In 1992, Congress ruled that all assassination documents can be released within 25 years, unless the president asserts that doing so would harm intelligence, law enforcement, military operations or foreign relations.
The National Archives has until Oct. 26 to disclose the remaining files related to Kennedy's 1963 assassination, unless Trump intervenes.
The Trump administration has been questioned for weeks as to whether the president would allow the documents to be declassified. The CIA and FBI, whose records make up the bulk of the batch, have declined to say whether they've appealed to the Republican president to keep them under wraps.
The still-secret documents include more than 3,000 files that have never been seen by the public and more than 30,000 that have been released previously, but with redactions.
"The American public deserves to know the facts, or at least they deserve to know what the government has kept hidden from them for all these years," said Larry Sabato, director of the University of Virginia Center for Politics and author of a book about Kennedy.
"It's long past the time to be forthcoming with this information," he added.
t's unlikely the documents contain any big revelations about Kennedy's killing, said Judge John Tunheim, who was chairman of the independent agency in the 1990s that made public many assassination records and decided how long others could remain secret.
The files that were withheld in full were those the Assassination Records Review Board deemed "not believed relevant," Tunheim said.
Its members sought to ensure they weren't hiding any information directly related to Kennedy's assassination, but there may be nuggets of information in the files that they didn't realize was important two decades ago, he said.
"There could be some jewels in there because ... our level of knowledge in the 1990s is maybe different from today," Tunheim said.
The Warren Commission — the body established by President Lyndon B. Johnson to investigate Kennedy's killing — found gunman Lee Harvey Oswald solely responsible for the president's assassination in 1963.
Kennedy was shot while riding in a presidential motorcade through downtown Dallas in a moment captured by video cameras. He was 46.
Five decades later, conspiracy theories still swirl around the young president's death and who was behind it.
Even a full release of the documents is unlikely to put those rumors to rest.
"People will probably always believe there must have been a conspiracy," Tunheim said, adding, "I just don't think that the federal government, in particular, is efficient enough to hide a secret like that for so long."