Soviet leader Mikhail Gorbachev declared Monday, "the road to truth is the only one," and condemned crimes of the Stalin era that led to mass deportations of Poles and the execution of Polish communists.

In a speech to the Sejm, Poland's parliament, on the first day of his visit to Poland, Gorbachev said a joint investigation would continue until several "blank spots" in Polish-Soviet history are cleared up.But he declined to admit Soviet responsibility for or even mention Katyn, the name of the Soviet forest where 4,250 Polish officers were massacred during World War II - the greatest "blank spot" of all.

"The road to truth is the only one - investigation of facts, factual comparisons of viewpoints, scientific discussions," Gorbachev said in reference to a joint Soviet-Polish commission set up last year at his initiative to investigate a series of Stalinist purges and other actions that have never appeared in official history books.

"Truth and justice may come late - but they must come," he said as his host, Polish leader Gen. Wojciech Jaruzelski listened, chin in hand.

Gorbachev condemned "Stalinist repressions" that resulted in the dissolution of the Polish Communist Party in the late 1930s and the deportations of more than 1 million Poles after World War II, when the Soviet Union shifted its borders westward to incorporate former Polish territory.

In a significant gesture on his arrival Monday at the Warsaw airport, Gorbachev stopped for a moment in the reception line to talk with Jarema Macieszewski, the Polish head of the Soviet-Polish commission investigating the "blank spots."

Gorbachev then left the formal reception line to work the crowd waiting at a fence, chatting and signing a few autographs.

"Nice, sunny weather," he said. "I am enjoying my visit."

Reflecting a popular soft drink commercial, a banner declared: "Perestroika: This is it" at the airport, where Gorbachev

stepped from an Aeroflot jet and was greeted by Jaruzelski, Prime Minister Zbigniew Messner and other Polish leaders.

Gorbachev's motorcade made several unlisted stops along the way into town from the airport so he could mingle with crowds - in most cases pre-arranged - and sign copies of his book, "Perestroika."

"I see the eyes and faces of Poles," he said at one stop. "I understand and see that you have a friendly approach to us. I understand how important the rapprochement is. We'll do our best with Comrade Jaruzelski so that our people can live better."

Activist sources said at least 10 dissidents, members of groups calling for a sovereign Poland independent of Soviet influence, were detained Sunday and accused of planning to disrupt Gorbachev's visit.

Gorbachev is the first Soviet leader to be genuinely popular among many Poles, who remember with bitterness the Stalin years when thousands of Poles were forced into Siberian exile during World War II.

The still unexplained disappearance of 15,000 Polish officers on Soviet territory during the war is perhaps the biggest "blank spot" in Polish-Soviet relations, and the outlawed Solidarity union and other dissident groups have called on Gorbachev to use the visit to admit they were killed by Russians.

Poland is the Soviet Union's largest Eastern European ally and Gorbachev's visit is the first official state visit by a Soviet leader since Leonid Brezhnev in 1972.

Gorbachev has been to Poland twice before as Soviet leader - for a Warsaw Pact summit and the Polish Communist Party congress in 1986 - but this is his first official state visit.

Gorbachev's four-day state visit will be followed by a two-day Warsaw Pact summit at which the East Bloc is expected to announce a new initiative on conventional arms reductions that may include a partial withdrawal of Soviet troops from an East Bloc state.

There is growing speculation the Soviet-led military alliance will use the Warsaw Pact summit to announce a partial withdrawal of Soviet troops from Hungary, Poland or East Germany .