Under pressure from Congress, the Justice Department and other agencies may be forced to declassify top-secret documents describing the U.S. intelligence community's dealings with Nazi war criminals in the Cold War years.

Legislation to open most of those files already has passed the Senate and could come up for a vote in the House this week.Some historians suspect the opened files could cause "tremendous embarrassments" for the United States.

"This potentially is the biggest series of revelations since the Nuremberg (war crimes) trials," said historian Robert Herzstein, speaking by telephone from his office at the University of South Carolina.

Herzstein and some other historians already have partly penetrated the wall of secrecy erected by the CIA, the FBI, the State Department and other agencies that hold the files, but many remain veiled in secrecy.

For half a century, federal agencies have resisted opening the files, telling historians, journalists, lawmakers and Holocaust survivors that national security was at stake and that promises previously made to "intelligence assets" made it impossible.

Still, Sen. Daniel Patrick Moynihan, D-N.Y., who with Sen. Mike DeWine, R-Ohio, sponsored the legislation, said the documents "have been held far too long, well beyond when the time when their disclosure might have posed a threat to national security."

"Those who suffered from the Holocaust are reaching the end of their life span. We owe it to them to make available as much information about that terrible period as possible," Moynihan said.

Jacob Hennenberg, a 74-year-old Holocaust survivor from Poland who spent four years in a concentration camp and lost dozens of relatives to the Nazis, agreed.

"If the U.S. government would come out with all this information that is hidden, maybe that would help to ease the pain of knowing that you can't do anything," he said from his home in Cleveland.

Many Nazis, including the infamous "Butcher of Lyons," Gestapo official Klaus Barbie, escaped occupied Europe following World War II "and got to South America with the help of U.S. authorities, like the counterintelligence corps of the U.S. Army," Herzstein, the historian, said. Barbie was convicted of crimes against humanity in France in 1987 and later died in prison.

In another example, the State Department and other agencies for a decade have told Herzstein that national security concerns bar them from releasing documents on the government's relationship with Kurt Waldheim, a former president of Austria and a former United Nations secretary-general.

Herzstein is questioning the government's role in concealing Waldheim's past as a Wehrmacht intelligence officer in the Balkans, where thousands of Nazi victims were deported to death camps.