More than 2800 files about US president John F Kennedy's assassination have been released at the order of Donald Trump, but he has yielded to FBI and CIA pressure to hold back some information.
Congress had ordered in 1992 that all records relating to the investigation into Kennedy's death should be open to the public, and set a final deadline of 26 October, 2017, for the entire set to be made public.
Mr Trump initially said on Saturday he would allow the 5,000,000 pages of documents to be made public.
Read the records on the National Archives Website.
Administration officials said Mr Trump ordered government agencies to study the redactions in the documents over the next 180 days to determine whether they needed to remain hidden from the public.
The officials described Mr Trump as reluctant to accept agency requests to hold back thousands of documents but felt in the end he had no choice but to agree to their entreaties.
"The president wants to ensure there is full transparency here and is expecting that the agencies do a better job in reducing any conflicts within the redactions and get this information out as quickly as possible," one official said.
Another official said sensitive information remained in the records that could compromise the identity of informants or intelligence operations.
More than 90 percent of the files were already in the public domain.
Academics who have studied President Kennedy's slaying in 1963 said earlier they expected the final batch of files to offer no major new details on why Lee Harvey Oswald gunned down the first and only Irish-American Roman Catholic to hold the office.
They also feared that the files will do little to quell long-held conspiracy theories that the 46-year-old president's killing was organised by the Mafia, by Cuba, or a cabal of rogue agents.
Thousands of books, articles, TV shows and films have explored the idea that Kennedy's assassination was the result of an elaborate conspiracy. None have produced conclusive proof that Oswald, who was shot dead two days after killing Mr Kennedy, worked with anyone else, though they retain a powerful cultural currency.
"My students are really skeptical that Oswald was the lone assassin," said Patrick Maney, a professor of history at Boston College. "It's hard to get our minds around this, that someone like a loner, a loser, could on his own have murdered Kennedy and changed the course of world history. But that's where the evidence is."
The documents released today would likely focus on efforts by the Central Intelligence Agency and Federal Bureau of Investigation to determine what contact Oswald had with spies from Cuba and the former Soviet Union on a trip to Mexico City in September 1963, experts said.
"There was a real concern that Oswald was maybe in league with the Soviet Union," Mr Maney said.
Mr Kennedy's assassination was the first in a string of politically motivated killings, including those of his brother Robert Kennedy and civil rights leader Martin Luther King Jr, that stunned the United States during the turbulent 1960s.