LVIV, Ukraine (AP) -- Drawing huge crowds near his Polish homeland, Pope John Paul II appealed Tuesday for a spirit of forgiveness across Eastern Europe, saying Christians need to recognize the misdeeds of a "sorrowful past."

Organizers estimated 600,000 people attended the pope's open-air Mass on a muddy racetrack in the western Ukrainian city of Lviv, by far the largest turnout since John Paul arrived in Ukraine on Saturday for a five-day visit.

Forty miles east of the Polish border, in a city that for centuries was part of Poland, it seemed like a homecoming. Pilgrims waved red and white flags in honor of Poland's favorite son, and most of the Mass was said in Polish.

The frail 81-year-old pope, last in his homeland two years ago, seemed energized by the reception in Lviv, the Catholic center of mainly Orthodox Christian Ukraine.

In high sprits as he braved a rainstorm later for a youth rally that drew about 300,000 people, John Paul sang part of a Polish folk song urging the rain to stop before warning of the temptations of Western consumerism and the illusions of an "easy life abroad."

Ukraine has lost many young professionals through emigration since gaining independence in 1991, while many young women have been enticed abroad and forced to work as prostitutes.

"Do not go from the slavery of the communist regime to the slavery of consumerism," the pope said, his white robes blowing in a stiff wind and both hands trembling sharply, a symptom of Parkinson's disease.

Young people at the rally welcomed his message of spirituality and unity.

"We need a moral and spiritual renewal in Ukraine," said Andriy Moskaliuk, a 23-year-old computer engineer.

When the setting sun finally emerged from behind the clouds, John Paul sang another Polish song and told his flock: "The sun shall shine in the end."

At the Mass earlier, the pope touched on problems facing Eastern European countries trying to rebuild following the fall of communism a decade ago and troubled through the centuries by nationalist, religious and political rivalries.

"Let us feel ourselves gently nudged to recognize the infidelities to the Gospel of not a few Christians of both Polish and Ukrainian origin living in these parts. It is time to leave behind the sorrowful past," he said in his homily.

"May pardon, given and received, spread like a healing balm in every heart. May the purification of historical memories lead everyone to work for the triumph of what unites over what divides, in order to build a future of mutual respect, fraternal cooperation and true solidarity," he said.

In addition to the religious and ethnic fissures that run through Eastern Europe, John Paul appeared to be addressing the issue of people affiliated with the atheist, communist regime of Soviet-era Ukraine.

Neither Ukraine, Russia nor any other former Soviet republic outside the Baltics has prosecuted former high-ranking communist officials for alleged crimes against the nation. Nor have they exposed former KGB informers, including in the churches.

The enthusiastic welcome as the pope crisscrossed the sun-dappled field in his popemobile in Lviv for the Mass was in stark contrast to the cool reception and thin crowds that greeted him in the capital Kiev, where Orthodox believers predominate.

Lviv is Ukraine's stronghold of Catholicism, and many inhabitants who suffered for their faith in Soviet times today are enjoying a religious renaissance -- exemplified by the first papal visit to Ukraine, which has been independent for 10 years.

"It's such a great event, he makes us so happy. This is something that happens once in a century, no, once in a thousand years," said Julia Hlovatska, 19, who had arrived at the Hippodrome Mass site at 2 a.m. after riding a train from the western town of Khmelnytskyi.

The papal trip pays tribute to the suffering of Ukraine's 6 million Catholics, most of them adherents of the Greek Catholic faith who practice Orthodox ritual but bear allegiance to the pope. Greek Catholic believers faced persecution under both Russian imperial and Soviet rule.

John Paul beatified two Roman Catholic clergymen on Tuesday and was to beatify more than two dozen Greek Catholics on Wednesday, most of them considered martyrs under communism.

Security at the Hippodrome was tight. The primate of Poland, Cardinal Josef Glemp, and Italian Cardinal Camillo Ruini had to remove their pectoral crosses to pass through the metal detectors.

Tens of thousands of pilgrims from Poland poured into Lviv for the visit. The relics of a Polish saint, John of Dukla, were brought from Poland and placed on the papal altar.

"It's so close to Poland that we just could not miss it," said Krzysztof Wojtalewicz, 39, a lawyer from Warsaw.

John Paul wants to heal the schism that has divided Christianity between the Catholic and Orthodox churches since 1054, and aides say he still hopes to visiting Russia someday.

But Russian church leaders refuse to meet with the Pope, pointing to bitter disputes over church property between Orthodox and Greek Catholics, which have sometimes spilled over into physical confrontations.