When Germany's highest court last year upheld her family's claim to one of several Berlin land parcels lost under the Nazis, Barbara Principe thought her legal battle was over. Principe, a 73-year-old great-grandmother from the US state of New Jersey, is the oldest living heir of the Wertheim family, which ran six department stores in Berlin until the 1930s.

Last month, a German federal agency decided that the claim also extended to prime land at Potsdamer Platz, the newly rebuilt center of reunified Berlin.

Principe and the Jewish Claims Conference, which represents the families, have expressed their interest to negotiate with German retail giant KarstadtQuelle, which was given the plot by Berlin after reunification but sold it later to another business group. But company officials say they will pursue every possible court appeal.

KarstadtQuelle spokesman Jörg Howe said on Monday that the company would face lawsuits from its stockholders if it negotiated now.

"We have to resolve this matter by court… as long as there is any doubt about who is the rightful owner of this property," Howe said. "It's no insult to the family history It's a very complicated matter."

Most complicated case

But in a press conference Monday at the Ritz Carlton hotel, which stands on the disputed land, Principe said the Wertheim heirs were determined to get back what their ancestors lost. To drive home that point, she brought along two of her grandsons, Michael Principe, 27, and Brad Giordano, 23.

"Even if I personally do not see the day, in my heart, I know my family is going to win," Principe said.

The Wertheim claim is among the largest and most complicated of the thousands of Nazi-era reparation claims pending in Germany.

It involves about 25 acres of land that Principe's lawyers say could be worth up to 500 million euros ($635 million), most of it situated in an East German no-man's land until the Berlin Wall fell.

About half the land has been settled in the Wertheim heirs' favor. The families have so far been paid around 70 million euros, according to Matthias Druba, Principe's Berlin attorney.

But the heirs also await compensation from the sale of one of central Berlin's largest undeveloped parcels of land, on nearby Leipziger Platz. The rest of the property is still tied up in court.

A web of owners

Among the most valuable is the five-acre Potsdamer Platz property known as the "Lenne Triangle," now a tony hotel and office complex. In August, the German federal agency that deals with property matters decided that the Jewish Claims Conference, which represents the heirs, had a claim on the land.

The Lenne Triangle's ownership line is complex. KarstadtQuelle bought the remnants of the Wertheim company in 1994, then sold it to developer Otto Beisheim for 145 million euros ($184 million).

Druba said that the longer KarstadtQuelle takes to settle the matter, the more they will owe in increased property value to the Wertheim heirs. But Principe said it is less about the money than about finding justice for her late father.

The family fled Germany in 1939, when Principe was six years old. Her father, Gunther Wertheim, died in 1954 as a chicken farmer who never told his daughter that the family once had Jewish roots or was a department-store dynasty. She found out years later from lawyers.

"I'm fighting, in a sense, for him, and for the family," she said. "This is our heritage."