REUTERS - Russian President Vladimir Putin will not join world leaders gathering at the site of the Auschwitz death camp this month because distrust caused by the conflict in Ukraine has cast a pall on arrangements to commemorate the Holocaust.

The Nazi camp where about 1.5 million people were killed, most of them Jews, became a symbol of the horrors of the Holocaust and a war that ravaged Europe. Seventy years later, conflict and political division are hampering preparations to mark the anniversary of its liberation.

Host country Poland - one of the most vociferous critics of Moscow over the Ukraine crisis - did not send a full diplomatic invitation to Putin, wary of the domestic political consequences of inviting the Russian leader, according to sources briefed on arrangements for the Jan. 27 event.

Moscow, in turn, was upset by what it viewed as a slight by Warsaw and has therefore not made plans for the president to attend, said the sources, who declined to be named due to the diplomatic sensitivity of the matter.

Putin's absence would stand out, especially as it was Soviet troops who liberated the camp in southern Poland in 1945, and many of the Jews killed in the Holocaust were Soviet citizens.

"The victory over Nazism depended on the collective engagement of many countries, the allies in the West but also the Soviet army," said a senior source in the European Jewish community, who spoke on condition of anonymity.

"For politics to interfere to exclude one country or another is a tragic shame to the memory of the Holocaust."

Poland's foreign ministry said it was not the organizer of the event but that no country was excluded from taking part. Kremlin spokesman Dmitry Peskov said at the moment he could not confirm Putin would be going, but said the president's decision would not be affected by any stance taken by Warsaw and that he did not feel slighted over the arrangements.

The row over Russian representation at the 70th anniversary event revolves around the subtleties of diplomatic protocol.

Formal invitations to foreign delegations were sent not by the Polish government but by the Auschwitz-Birkenau State Museum and International Auschwitz Council, the joint organizers.

According to a source involved in negotiations over the event, the Polish government sent foreign states what is called a "note verbale" about the Auschwitz events - a notification which falls short of being a formal invitation.

The source said Poland chose that format because it would have been unpopular among voters at home for the authorities to send Putin a formal invitation, in a year when presidential and parliamentary elections will take place.

Many ordinary Poles view the Kremlin with suspicion, opinion polls show, a sense heightened since Russia annexed the Ukrainian region of Crimea last year and pro-Moscow militias in eastern Ukraine rebelled against Kiev's rule.

Warsaw has lobbied fellow EU states for tougher sanctions on Russia and pressed for a bolder response from NATO. Moscow reciprocated by banning imports of many Polish food products.

"It's not going to happen," the source said of the attendance of Putin, who 10 years ago had joined leaders at Auschwitz to mark the 60th anniversary.

A Polish government source, speaking on condition of anonymity, also said Putin was unlikely to come because Poland had not sent a full diplomatic invitation.

A source close to Poland's ruling party said the "climate" was not right for Putin to come.

The Polish foreign ministry told Reuters: "The Polish government has played no role in sending invitations to any third parties."

"The ministry of foreign affairs would also like to underline that it is up to the Russian authorities to decide on the level of representation at the Auschwitz commemorative event. Everyone wishing to participate will be welcome."

The ministry did not respond directly to questions about the note verbale, whether the state wanted Putin to attend, and whether political considerations were influencing arrangements.

A spokesman for the Auschwitz Museum said he could comment on the composition of foreign states' delegations.

In the neighboring Czech Republic, President Milos Zeman, a critic of sanctions against Russia who has expressed sympathy with Moscow's position on Ukraine, invited Putin and leaders of the other World War Two allies to a separate, smaller, Holocaust commemoration on the same day as the Auschwitz event.

But the invitation to Putin angered many Czechs. The Czech Federation of Jewish Communities distanced itself from the invitation, citing Russia's role in Ukraine. No foreign heads of state have confirmed they will be at the Czech event.