EAST RUTHERFORD, N.J. (AP) _ Invoking Emma Lazarus' plea for America to embrace the huddled masses, Pope John Paul II urged the nation Thursday to welcome immigrants and rid itself of the ``moral blight'' of abortion and euthanasia.

Just 10 miles from the Statue of Liberty, the pontiff told 82,948 rain-soaked worshipers _ a Giants Stadium record _ to continue in the tradition of the civil rights movements to extend legal protection to ``the unborn child,'' the elderly and the severely disabled.

``Both as Americans and as followers of Christ, American Catholics must be committed to the defense of life in all its stages and in every condition,'' the pontiff declared from a giant altar at one end zone.

In addition to his criticism of liberals' attempts to expand access to abortion and to permit assisted suicides, the pope was critical of recent conservative efforts to limit immigration.

He recited part of Lazarus' 19th century poem in urging Americans to continue to welcome immigrants yearning to breathe free and to serve the poor.

``If America were to turn on itself, would this not be the beginning of the end of what constitutes the very essence of the `American Experience?' '' he asked in his homily.

Hours of steady rain and raw October weather could not detract from the enthusiasm of the huddled masses inside the converted football field. Some wept, others pressed their hands to their hearts or cried ``Viva el Papa'' as the pontiff circled the stadium in his popemobile.

``This is the most important day of my life. I cannot describe to you how important it is to be here,'' 76-year-old Edward Pietro of Toms River said. ``After today, if nothing else exciting or wonderful happens in my life, I will die a fulfilled man.''

Earlier, the pope urged the United Nations to be an authentic force for peace.

``The United Nations Organization needs to rise more and more above the cold status of an administrative institution and to become a moral center where all the nations of the world feel at home,'' he told the 185-member General Assembly.

The pope's visit during the United Nations' 50th anniversary year was the central point of his fourth pilgrimage to the United States. The organization is deeply in debt, in part because of its expanded peacekeeping operations in Bosnia and elsewhere, and John Paul wants to see it strengthened.

But that meeting like the other events since the pope's arrival Wednesday was for a small group of dignitaries and invited guests. It was here in Giants Stadium that masses of the faithful could see the man many believe is the vicar of Christ on Earth.

Among them was Donna Tellicano, who suffers from multiple sclerosis and uses a wheelchair. She came hoping that the pope would touch her and miraculously cure her.

Andrew DiDomenico, a 24-year-old bagel baker from Clifton, came because ``God wanted me to be here.''

``I was here in the rain for quite a few Grateful Dead shows. I was here for that, I should be here for this,'' he said.

After the Mass, 68-year-old Ada Tronolone of Toms River said she could not describe how exhilarated she felt.

``Seeing John Paul II was a personal experience in a crowd of more than 80,000. He makes you feel like he's just talking to you,'' she said.

In an atmosphere more resonant of a concert or athletic event than a Mass, flashbulbs popped throughout the stadium as the pope re-entered the field for the opening procession.

Before that, worshipers did ``the wave'' and chanted ``John Paul II, we love you'' as they waited.

The pope was partially protected by a white canopy hanging over a huge red-carpeted altar set up in an end zone. But at one point, the wind knocked off his white skullcap. Some bishops celebrating Mass with the pope wore clear rain slickers over their white and gold vestments.

At the United Nations, John Paul sketched the dramatic changes since he last addressed the assembly in 1979 _ the fall of Communism and cuts in nuclear arsenals.

Now, he stressed, the danger stems from a ``narrow and exclusive nationalism,'' which triggered ``a true nightmare of violence and terror,'' most recently during ethnic upheavals in Rwanda and Bosnia.

``Nationalism, particularly in its most radical forms, is thus the antithesis of true patriotism, and today we must ensure that extreme nationalism does not continue to give rise to new forms of the aberrations of totalitarianism,'' he said.

Touching on a theme he raised during a trip to Africa last month, the pope said developing countries often face ``a situation of de facto economic dependence on other countries. Such situations offend the conscience of humanity and pose a formidable moral challenge to the human family.''

``We have within us the capacities for wisdom and virtue,'' he continued. ``And in doing so, we shall see that the tears of this century have prepared the ground for a new springtime of the human spirit.''

Even at the austere U.N. headquarters alongside New York's East River, the visit evoked a warmth rare in such formal surroundings.

As the 75-year-old pontiff approached, U.N. employees stood on furniture and hopped up and down with cameras raised over their heads. Their shouts echoed through the stone and glass hall.

Children from the United Nations International School, many dressed in clothing that reflected their ethnic backgrounds, greeted the pope in the lobby. One child held a papier-mache white dove. The pope lifted the symbol of peace and asked the children to ``pray for ... humanity.''

At other stops during his four-hour stay at U.N. headquarters, the pontiff dedicated a plaque to U.N. personnel killed while on peacekeeping duty or on humanitarian missions.

John Paul's trip runs through Sunday night, and is to include huge Masses in Central Park in Manhattan and Aqueduct Race Track and at Camden Yards baseball stadium in Baltimore.