Three days of commemorations have begun in Warsaw marking the 60th anniversary of the uprising by Polish partisans against Nazi occupiers.
More than 200,000 civilians were killed and Warsaw was left in ruins.
Gerhard Schroeder will be the first German chancellor to attend the annual ceremonies when he visits on Sunday.
Poland's prime minister called on him to dismiss calls for reparations from ethnic Germans driven out of Poland at the end of World War II.
The commemorations will take place over three days, culminating in Sunday's anniversary.
'Bad atmosphere'
Prime Minister Marek Belka told Germany's Die Welt newspaper that Mr Schroeder's visit was of "huge importance" to Poland.
He said there was a "bad atmosphere" between their two countries, and urged his German counterpart to dispel it.
Mr Belka said it would send a powerful message if Mr Schroeder used the anniversary to speak out against reparation claims by Germans expelled from Poland.
"The bigger and stronger neighbour must always show greater sensitivity," he said.
Mr Belka said he did not suggest the chancellor should drop to his knees - as his predecessor Willy Brandt did in 1970 in a gesture of humility at the site of the 1943 Jewish rebellion in the Warsaw ghetto.
"We do not expect him to kneel but we expect good words," he said.
The partisan uprising broke out at 1700 on 1 August, 1944.
At the time, its commanders estimated they could hold out for about five days without help.
Against a vastly better-equipped German army, the insurgents held out for much longer - 63 days. Its leaders were counting on help from the rapidly advancing Soviet army, which had just reached the outskirts of Warsaw.
Alone
The partisans also believed their Western allies, Britain and the United States, would provide assistance. In the end, very little arrived.
The Red Army halted its advance and observed the battle from the other side of Warsaw's Vistula River.
They sat and watched as the SS commanders carried out Hitler's orders to level the city and kill or deport its inhabitants.
A whole generation of leaders was wiped out. Months later, the Soviet army took over a city of rubble.
Stalin also installed a puppet government - a new occupation which would last for more than four decades had begun, says Professor Norman Davies, the author of a new history of the rising.
"This is, I think, what the Warsaw rising reminds us about - the end of World War II was very painful for many people, especially in the eastern part of Europe," he said.
The anniversary will be marked by wreath-laying and concerts, as well as the opening of new, interactive Rising museum.
As he did for the D-Day celebrations in Normandy, Mr Schroeder, will also take part, alongside US Secretary of State Colin Powell and Britain's Deputy Prime Minister, John Prescott.
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