The German and Russian leaders are expected to discuss the fate of a Rubens masterpiece looted during World War II when they meet this week.
Russian President Putin (right) is meeting German Chancellor Schroeder
The painting, Tarquin and Lucretia, is believed to have been stolen from Germany by a Soviet officer in 1945.
It has resurfaced after being offered for sale by a Moscow estate agent.
Its return is expected to be raised when German Chancellor Gerhard Schroeder and Russian President Vladimir Putin hold a two-day summit.
The masterpiece is thought to have been painted between 1606 and 1612 and was originally bought by Frederick the Great in 1765 and displayed at his palace near Berlin.
But at the end of World War II, when Soviet troops threatened Berlin, Nazi propaganda minister Joseph Goebbels had it moved to Rheinsberg Castle 80km away.
The Foundation for Prussian Palaces and Gardens in
Berlin-Brandenburg (SPSG), which manages Sanssouci, was made aware that the painting had resurfaced when it was sent an email offering it for sale earlier this year.
It traced the painting to Russia and alerted the German government.
The Moscow estate agent trying to sell it, Vladimir Logvinenko, said he bought the painting legitimately on the open market.
Germany now wants it returned but officials in Berlin have refused to consider compensation, saying it would legitimise its theft.
One options is that Mr Putin - who is meeting Mr Schroeder in the city of Yekaterinburg on Wednesday and Thursday - will present the painting as a gift to the Germans.
Another option is that Germany will go through a lengthy legal case for its return.
The painting, which shows the rape of Lucretia by Roman emperor Tarquin, is said to be in poor condition.
"The scarring will endure," SPSG director Burkhardt Goeres said. "But we are glad that it was rediscovered and that it still exists."
According to the SPSG, more than 3,000 pieces of work disappeared from Germany at the end of the war.
Russian Culture Minister Mikhail Shvydkoi hinted that the
government would authorise the painting's return if the state prosecutor's office approved it.