MOSCOW — Prime Minister Vladimir V. Putin, in Poland to mark the 70th anniversary of the start of World War II, praised Polish soldiers and citizens on Tuesday for their wartime bravery, even as the Russian government unveiled what it said were previously classified documents showing prewar Polish cooperation with Nazi Germany.

Mr. Putin’s remarks appeared aimed at dampening a row between Russia and Poland over each country’s role in the war, a dispute that grew heated in the weeks before the anniversary.

“Russia has always respected the bravery and heroism of the Polish people, soldiers and officers, who stood up first against Nazism in 1939,” Mr. Putin said in a meeting with the Polish prime minister, Donald Tusk, in the Baltic Sea resort town of Sopot.

Mr. Tusk said Mr. Putin’s visit reflected a growing spirit of cooperation despite lingering disagreements.

“Our meeting showed from the first minute that we are making another step toward strengthening confidence in the past so that we can build our future on it,” Mr. Tusk said in remarks translated into Russian on Mr. Putin’s Web site.

The relative warmth stood in contrast to Polish frustrations with the United States; Mr. Tusk has taken pains to play down the fact that President Obama was represented at the memorial ceremonies by his national security adviser, which many Poles saw as a snub.

Poland’s traditionally close relations with Washington are already being tested by reports that the Obama administration is reviewing the Bush administration’s plan to deploy parts of its antiballistic missile shield in Poland, as well as the Czech Republic, two Eastern European states eager for the American presence, particularly as Russia has grown more aggressive internationally.

Moscow has opposed having the missile shield in Eastern Europe. Mr. Putin’s remarks on Tuesday could have been intended to exploit Poland’s frustration with Washington to repair the Kremlin’s relationship with Warsaw.

Many in Poland are angered by what they see as Russia’s failure to acknowledge atrocities committed by the Soviet Union — including the massacre of Polish soldiers in the Katyn Forest and mass deportations — after its troops occupied eastern Poland weeks after the Nazis invaded the west of the country.

At a service attended by Mr. Putin in Gdansk on Tuesday, Poland’s president, Lech Kaczynski, remarking on the Soviet invasion, said Moscow had “stuck a knife in the back of Poland,” according to Agence France-Presse.

Such sentiments have incensed many Russians, who view World War II and the victory over the Nazis as a paramount event in their history. By some estimates, about 25 million Soviet citizens died in the war, and many here believe those sacrifices were made to liberate Eastern Europe, not occupy it. About two-thirds of Russians think the Soviet Union could have defeated Nazi Germany alone, according to a recent poll of 1,600 people by the Russian Public Opinion Research Center that had a margin of sampling error of plus or minus about three percentage points.

Attempts by Poland and other former Communist bloc countries to equate Nazi crimes and Soviet actions during the war have prompted a Russian backlash. A documentary on Russian state television last week claimed that, in the 1930s, Poland conspired with Germany and Japan to invade the Soviet Union. Meanwhile, President Dmitri A. Medvedev has created a panel to fight what the government says are falsifications of history that harm Russia’s image.

On Tuesday, Russia’s Foreign Intelligence Service unveiled archival documents said to show Polish cooperation with Nazi Germany before the war and Polish attempts to sow discord among the Soviet Union’s ethnic nationalities.

“Without a doubt, a portion of the blame for unleashing the Second World War lies with Poland, which is why they are attempting to distort historical fact,” Lev F. Sotskov of the Foreign Intelligence Service told reporters in Moscow.

Polish journalists challenged the documents’ authenticity, asking why the Russian government had waited decades to unveil them, only to do so during Mr. Putin’s visit. For those who questioned if the documents were genuine, Mr. Sotskov said, “It’s their problem.”

In Poland, however, Mr. Putin seemed to step back from historical debates, describing a shared failure to prevent “the bloodiest, most horrible war in the history of humanity.”

“All attempts between 1934 and 1939 to make peace with the Nazis, signing various agreements and pacts, were from a moral point of view unacceptable and from a practical point of view pointless, harmful and dangerous,” he said at the Gdansk memorial service. “It is necessary to admit these mistakes, and our country has done this.”

The remarks followed an article by Mr. Putin published on Monday in the Polish newspaper Gazeta Wyborcza, which characterized the Nazi-Soviet pact to divide Poland at the outset of World War II in 1939 as immoral.

Mr. Putin’s performance in Poland drew praise from many erstwhile critics of Russia, if not completely fulfilling Polish demands for Russian accountability.

“This is a very important and very symbolic visit,” said Andrzej Halicki, chairman of the Polish Parliament’s Foreign Affairs Committee. He said Mr. Putin’s statements left him optimistic about the future of their countries’ relations, but added, “This would have been a good occasion to say ‘sorry.’ ”

Judy Dempsey contributed reporting from Berlin.