Russia's Vladimir Putin will be absent from the main event marking 70 years since Soviet troops liberated the Auschwitz death camp in Poland, held against a backdrop of hostilities in Ukraine and warnings of a rise in anti-Semitism in Europe.
The commemoration on Tuesday at the site in southern Poland where the Nazis killed about 1.5 million people, mainly European Jews, between 1940 and 1945, may be the last major anniversary when survivors attend in numbers. The youngest are in their 70s.
Around 300 are expected to make the trip, down from 1,500 ten years ago when Mr Putin was among the visiting heads of state and government.
Poland is one of the most vociferous critics of Russian actions in neighbouring Ukraine, where Moscow annexed Crimea last March after the ouster of Ukraine's then Kremlin-backed president. Russia is accused by Nato of sending troops and armour to aid pro-Russian separatists in the east.
The war, in which at least 5,000 people have been killed, has been fought in language recalling World War Two. At the weekend, Donald Tusk, a former Polish prime minister who now chairs summits of European Union leaders, warned against the "appeasement" of Russia amid a renewed offensive by separatists.
Wary of the domestic political consequences, Poland did not send a full diplomatic invitation to Putin, sources said. His chief of staff, Sergei Ivanov, will attend instead.
Ukrainian president Petro Poroshenko is due to attend, as are France's Francois Hollande and Germany's Joachim Gauck in a day of prayer and wreath-laying at the site, now a museum.
Hollande makes the trip less than three weeks after Islamist gunmen killed 17 people in Paris in attacks on the Charlie Hebdo satirical weekly newspaper and a kosher supermarket.
Four French Jews were among the dead, the latest victims of a recent spate of armed attacks on Jews in Europe.
European Jews warn of a growing under-current of anti-Semitism, fuelled by anger at Israeli policy in the Middle East and social tensions over issues of immigration, inequality and economic hardship that have contributed to a rise of far-right political movements.
David Wisnia, an 88-year-old survivor of Auschwitz, said on Monday the Holocaust was “almost impossible for a human mind to comprehend.” A choir boy as a child at Warsaw’s Great Synagogue, which was blown up by Nazi forces in 1943, Wisnia will sing a memorial prayer in Hebrew on Tuesday.
“I pray to God that we as human beings are able to learn something from it,” he said.
Hollywood director Steven Spielberg, talking to Holocaust survivors in the southern city of Krakow on Monday, said: "If you are a Jew today, in fact if you are any person who believes in the freedom of religion, freedom of speech, freedom in free expression, you know that like many other groups, we are once again facing the perennial demons of intolerance."
Spielberg, whose films include Schindler's List about a German who saved more than a thousand mostly Polish-Jewish refugees during the Holocaust, said he hoped Tuesday's commemorations would act as a warning to future generations.
Agencies