The decision not to invite Russian President Vladimir Putin to last week's ceremony marking 70 years since the liberation of the Auschwitz concentration camp was a strategic mistake that will have harsh consequences on the US and EU's relations with Moscow, according to senior diplomats.A number of world leaders took part in the the ceremony at the camp in Poland. However, the Polish government initiated the decision not to invite Putin. According to diplomats, the Polish decision was coordinated with the US government, which fully supported the move. European countries appear to have expressed their silent support for the Polish move as well. Senior sources at the UN headquarters in New York said that Putin was so offended by the move that he is unlikely to let it go unpunished. "The US and Europe will strongly feel the response that Putin is preparing," a senior diplomat in New York said Tuesday.According to sources, Putin was not as upset with other US and European moves, which had political implications, such as the decision to not invite him to the G8 summit. Putin also made a point of not attending last year's meeting of the UN General Assembly - an international event the he used as a way of proving to his opponents in the West that there presence in New york did not impress him.However, the intentional move to exclude him form an international event meant to memorialize a central event of WWII - an event that was carried out by the Red Army, who liberated Auschwitz - was taken by Putin as an unforgivable slight that undermines the Russian narrative of the war and Fascism."To exclude Putin was like sticking a thumb in his eye," one diplomat said. "A stinging and painful move such as this, connected to Russia's part in defeating the Nazis, Putin will not take quietly."According to the sources, Putin will respond to the insult with steps connected to regional conflicts and crises, which Russia, as a world power and permanent member of the UN Security Council, has power to influence. Russia's moves are not likely to be appreciated by the US and its western allies."I would not be surprised if Russia exacerbates the conflict with the US on the issues of the continuing Syrian conflict and the future of Bashar Assad, and Putin expresses his rage by tampering with nuclear negotiations with Iran and the future of relations with Tehran," a diplomat said.Sources in New York estimate that recently renewed fighting in Ukraine between rebels and the government in Kiev is part of Putin's reaction to the diplomatic slap in the face that he perceived the lack of an Auschwitz invite to be.