The CIA has been urged to release documents about Nazi war criminals hired by US intelligence officials during the Cold War era.
Nazi soldier Klaus Barbie worked for Western intelligence after the war
The call comes from members of Congress who drew up the 1998 public disclosure law, which requires declassification of all documents about the Holocaust.
They say the CIA is withholding details of people it recruited after World War II for their expertise.
Released documents show links between US intelligence and Nazi war criminals.
The CIA has contributed 1.25 million pages of documents, of more than eight million, released under the 1998 law.
One former Nazi known to have been employed by Western intelligence was Klaus Barbie, the infamous "Butcher of Lyon". He was eventually convicted of crimes against humanity by a French court.
The law's authors - Senator Mike DeWine and Representative Carolyn Maloney - believe the CIA is withholding further details on the Nazi war criminals, suspects or collaborators that were hired.
"There is still information that we believe the CIA has about the United States' involvement with former Nazis," said Sen DeWine. "We need to get this information out."
He and Rep Maloney are due to discuss the matter with CIA officials on Tuesday.
According to the Associated Press news agency, Sen DeWine will lead a Senate Judiciary Committee hearing on the issue later in the month if an agreement is not reached.
"It has been 50 years and there is really no reason to keep this information secret at this point," he said. "We have to bring closure to this."
A CIA spokesman, speaking on condition of anonymity, acknowledged the agency was withholding some information, AP said.
He said the agency planned to submit a report to Congress, which is required in order to qualify for an exemption from releasing the documents.