U.S. Pushes Germany to Reveal Hoard of Nazi-Looted Art Marc Mueller / EPA The picture of a painting by German artist Franz Marc titled 'Horses in Landscape' is projected onto a wall during a press conference on the spectacular art find in Munich, Nov. 5, 2013. More than 20 months have passed since German authorities uncovered a hidden trove of hundreds of artworks that the Nazis looted during the Holocaust. Yet only 79 of those works, which were found in the apartment of Cornelius Gurlitt, the son of Adolf Hitler's art dealer, have so far been made public. The secrecy, intended to protect Gurlitt's right to privacy, has left many victims of Nazi confiscation unable to file claims for their art to be returned. Now, the apparent lack of transparency on the part of German authorities has urged the U.S. to start applying diplomatic pressure on behalf of Holocaust survivors and their heirs. "This list of artworks needs to be published," Stuart Eizenstat, the adviser to U.S. Secretary of State John Kerry on Holocaust issues, told TIME in an interview Wednesday. In 1998, more than 40 countries, including the U.S. and Germany, signed an agreement known as the Washington Principles, which outline necessary steps for the return of art looted by the Nazis. Serving at the time as Under Secretary of State in the Clinton Administration, Eizenstat organized and led the negotiation of that agreement on behalf of the U.S., and he insists that Germany is at risk of violating the principles by keeping Gurlitt's hoard from the public. "The basic principle," he says, "is that every effort should be made to publicize art that's found to have been confiscated by the Nazis and not subsequently restituted in order to locate their pre-war owners." MORE: Why the Man Who Hoarded Nazi-Looted Art May Get to Keep It All On Nov. 8, the U.S. embassy in Berlin issued an official démarche to the office of German Chancellor Angela Merkel, as well as the German Ministry of Justice and the Ministry of Culture, urging that the list of paintings found in Gurlitt's apartment be published, Eizenstat says. The U.S. embassy does not appear to have publicized that démarche, and an embassy spokesman could not immediately confirm when reached by TIME on Friday whether it had indeed been issued. Four days later, on Nov. 12, German authorities published 25 of the works on the government-run website LostArt.de, promising that the list would be "continuously updated." But the slow drip of the disclosures since then has not satisfied Eizenstat or the potential claimants waiting to see if their art works were among those found in Gurlitt's possession. References to Gurlitt's privacy, which is protected under German law, does not win much sympathy from Eizenstat. "Whose privacy is it they're trying to protect?" he says. The families want to know what happened to their art, the museums want to know what happened to their art. And he has no right to privacy if he got them, or his father got them, in an untoward way. Gurlitt's father, Hildebrand Gurlitt, is known to have helped the Nazis sell off the art they looted or confiscated from German museums and private collectors, most of whom were Jewish. The younger Gurlitt, in an interview published on Sunday, told the German weekly magazine Der Spiegel that his father had legally acquired all of the 1406 artworks from art dealers and museums, reportedly including works by Renoir, Picasso and Matisse. He also raised the issue of privacy, telling Der Spiegel: "What kind of government are they to show my private property?" MORE: Nazi-Art Bust: 6 Unanswered Questions On Thursday, the German newspaper Süddeutsche Zeitung reported that about 310 of the works would be returned to Gurlitt, citing the Bavarian prosecutor in charge of the case. These works are "undoubtedly the property of the accused," the prosecutor, Reinhard Nemetz, was quoted as saying. As for the rest of the works, their review will be completed next week at the latest, the prosecutor told Süddeutsche Zeitung. But fighting over the ownership of these works in German courts would be a losing struggle for Holocaust survivors, art lawyers and experts told TIME this week, as Gurlitt would be able to invoke Germany's statute of limitations for such cases to protect himself from civil lawsuits. That is part of the reason the Washington Principles laid out a restitution process not tied up in regular courts. After seeking out and publishing any art works suspected of being Nazi loot, Germany is mandated under that agreement to form a special government commission to review any claims to their ownership. In Gurlitt's case, if the commission finds that he is the legal owner, he gets to keep the artworks in question. If the ownership is in doubt, the commission can also rule that the art should be sold and the proceeds split between Gurlitt and the claimant. The principles envision a number of creative solutions, just and fair solutions. But none of that is possible without the initial publication," says Eizenstat. Without it, "You'd just be flying in the blind, because you wouldn't know what to negotiate." So far in the Gurlitt case, Germany does not appear to have complied with any of the steps in this process, even though it has been "exemplary" in implementing the Washington Principles over the past decade, says Eizenstat. However, since the Principles are not legally binding, the only thing foreign diplomats can do is apply moral and diplomatic pressure on Germany to comply. MORE: Russian Region Tolerates "Bride Stealing" Even After Triple Murder At the top of the federal hierarchy, that seems to be working. Numerous German ministers, as well as the spokesman for Chancellor Merkel, have called for urgency and transparency in the Gurlitt case since it began to draw international outrage earlier this month. The problem is with some of the Bavarian prosecutor's issues, like privacy and the tax evasion case. Suspected tax evasion is what led German authorities to search Gurlitt's apartment in February 2012, when they first stumbled upon his hoard of art. Since then, the prosecutors handling the investigation in Bavaria have continued to treat it as a case of tax evasion rather than of stolen or looted art. For Eizenstat, that reveals a weakness in the agreement he negotiated 15 years ago. "It indicates that subnational units like the Bavarian government have difficulty with the Washington Principles, which are principles subscribed to by the national governments," he says. So at the local level, the authorities are apparently able to keep Nazi loot under wraps - at least until the moral and political pressure from their superiors comes bearing down.