The United States wants the International Tracing Service's collection, one of the world's largest from the Nazi era which includes files on more than 17 million people, to be made available to historians.

Germany has so far refused to allow the archive at Bad Arolsen to be opened fearing it could lead to lawsuits claiming that personal details were given out illegally.

The German government and the tracing service insist the personal files, many of which refer to victims of the Holocaust, cannot be immediately released because of international agreements and German privacy laws.

A question of privacy

The government has maintained that the archives will be opened in time but not before privacy controls have been put in place. "Before opening the archives to researchers indiscriminately, questions of privacy and liability for the misuse of this sensitive data needs to be addressed," a German foreign ministry spokesperson told the New York Times.

Germany is coming under increased pressure from the US and Holocaust historians to release the files, and, last year, 20 countries published a joint statement backing the US position and called for the urgent release of the documents to researchers.

One American researcher has called the refusal to open the archive "a form of Holocaust denial."

The International Tracing Service, a branch of the International Committee of the Red Cross that was established to help families discover what had happened to their relatives, holds the documents which were gathered by Allied forces as they liberated Nazi concentration camps in the final days of World War II.

Secret programs and horrific experiments

The documents detail horrific medical experiments and include files on alleged collaborators among concentration camp inmates.

There is also comprehensive documentation on the Lebensborn program, under which tens of thousands of children born to women in Nazi-occupied countries and fathered by German soldiers were sent to special educational facilities, where they were raised to be part of the Nazis' so-called "master race."