SOPOT, September 1 (RIA Novosti) - Prime Minister Vladimir Putin told his Polish counterpart on Tuesday that the two countries must not let historical disputes over World War II come in the way of building cooperation.

Putin met with Donald Tusk at the seaside resort of Sopot near Gdansk, which is hosting ceremonies to mark the 70th anniversary of the outbreak of the war.

At least 20 world leaders gathered in Gdansk to remember September 1, 1939 when Nazi Germany attacked Poland at the start of the war. Poland and some ex-Soviet states blame a deal between Stalin and Hitler for the start of the war.

"As to what preceded the tragedy, that should be left to the experts to determine," Putin told Tusk. "We must understand what triggered the start of the war, and move on."

Russia has strongly resisted attempts to portray the Soviet Union as an aggressor in the war, in which it lost at least 27 million people. The 1939 Molotov-Ribbentrop Pact is believed by many to have opened the way for the invasion of Poland and the ensuing world war.

Speaking at a news conference after the talks, Tusk reiterated his government's official position: "The Molotov-Ribbentrop pact led, in one way or another, to the aggression against Poland. Germany attacked Poland on September 1, and two weeks later Stalinist Russia's troops came from the east."

Putin argued that it was unfair to claim the pact acted as the sole trigger for the war.

He urged for an unbiased approach to history: "We all have made a lot of mistakes. All of them contributed to the start of the large-scale aggression by Nazi Germany."

In an article published ahead of his Polish visit, Putin condemned the deal with Hitler, in which two countries pledged neutrality and agreed in a secret protocol to divide Northern and Eastern Europe, including Poland, into spheres of influence.

But Putin recalled the 1938 Munich treaty between major European powers and Hitler, which permitted the German annexation of Czechoslovakia's Sudetenland. He said Poland then sent its troops into Czech provinces.

Tusk, however, acknowledged the recent improvements in relations. "Relations between Poland and Russia are better now than ever. Although the crisis has led to a decline in [trade] turnover, we want the dynamics to be stronger."

Tusk said he and Putin agreed that energy must not be linked to politics. He said Poland looks to signing a new contract on Russian natural gas supplies this fall.

Poland consumes some 14 billion cubic meters of gas a year, 6.2 billion of which it imports from Russia. The country's own production stands at 4.2 billion cu m.

Putin, on his part, urged a corruption probe into the joint venture running the gas pipelines in Poland, expressing concerns about its ownership structure.