Oct. 3, the 20th anniversary of German unification, will also mark the completion of the final chapter of World War I with the end of reparations payments 92 years after the country's defeat.

The German government will pay the last installment of interest on foreign bonds it issued in 1924 and 1930 to raise cash to fulfill the enormous reparations demands the victorious Allies made after World War I.

Obama, who has promoted renewable energy, has come under pressure from environmentalists and the solar industry to install photovoltaic roof panels at the White House. President Jimmy Carter did so in 1979, but the panels were removed during the Reagan administration. President George W. Bush used solar energy to power a maintenance building on the grounds and heat the pool.