Israel hailed the World Holocaust Forum as the biggest international gathering in its history. Russian President Vladimir Putin and US Vice President Mike Pence are among the attendees.
Dozens of world leaders convene in Jerusalem on Thursday to mark the 75th anniversary of the liberation of Auschwitz amid a backdrop of rising anti-Semitism in Europe and the US.
However, the president of Poland, where the Nazi concentration camp was built during the German occupation of World War Two, will stay away due to rankling disputes with both Russia and Israel.
Israel has hailed the World Holocaust Forum the biggest international gathering in its history. Russian President Vladimir Putin and US Vice President Mike Pence are among the attendees.
Poland will host its own event at the Auschwitz-Birkenau Memorial and Museum on January 27.
More than one million people, most of them Jews, were killed at the Auschwitz-Birkenau camp. Six million Jews died in the Holocaust.
Speeches at the Jerusalem event are likely to focus on the horrors of the Nazi Holocaust, as well as a more recent rise in anti-Semitism rhetoric and attacks worldwide.
Anti-Semitic attitudes on the rise
A global survey by the US-based Anti-Defamation League in November found that global anti-Semitic attitudes had increased and significantly in Eastern and Central Europe. It found that large percentages of people in many European countries think Jews talk too much about the Holocaust.
Israeli President Reuven Rivlin addressed this at a reception he hosted on Wednesday for the visiting leaders.
"I hope and pray ... that the leaders of the world will stand united in the fight against racism, anti-Semitism and extremism, in defending democracy and democratic values," he said.
In Jerusalem, the high-profile guest list includes French President Emmanuel Macron, German President Frank-Walter Steinmeier and Britain's Prince Charles.
Polish President Andrzej Duda turned down an invitation to the conference, expressing dissatisfaction that representatives of Russia, France, Britain, the US and Germany would speak, while Poland was told it would not be allowed to.
Israeli organisers said only the four World War Two allies, and Germany, would address the gathering.
Polish leaders have also been angered by comments made by Putin last month suggesting Poland shared responsibility for the war.
Warsaw will be scrutinising speeches by Putin and Netanyahu, who Israel's Channel 12 TV reported might echo some of the Russian leader's accusations against Poland in return for the pardon of an Israeli woman imprisoned in Russia on drug charges.
"Above all, we are asking that the memory of the Holocaust, that terrible crime, the memory of its victims, is not exploited for political reasons. That would be vile," Poland's deputy foreign minister, Szymon Szynkowski vel Sek, said on Tuesday.
The international gathering could burnish Israeli Prime Minister Benjamin Netanyahu's domestic image as an international statesman. The veteran right-wing leader faces his third election in less than a year on March 2 amid legal woes and political deadlock.
Fighting for his political survival, Israel's longest-serving premier has been using sideline meetings with international leaders at the conference to call for more sanctions against arch-enemy Iran.
France, along with Britain and Germany, last week declared Iran in violation of a 2015 nuclear pact. They launched a dispute mechanism that could lead to the reimposition of UN sanctions lifted after the agreement to limit Tehran's atomic activities was signed.
French President Macron met Israeli and Palestinian leaders on Wednesday and toured Christian, Jewish and Muslim sites in Jerusalem, including the Church of St Anne, the Muslim Noble Sanctuary that houses al Aqsa mosque, a site revered by Jews as Temple Mount, and Judaism’s Western Wall.
Macron then headed to Ramallah for a meeting with Palestinian President Mahmoud Abbas, who issued a statement through the official Palestinian news agency calling upon European leaders to revive the long-stalled Mideast political peace process and "save the two-state solution."