VATICAN CITY, FEB. 19 -- Pope John Paul II accused the two superpowers today of betraying "humanity's legitimate expectations" through a continuing and negative rivalry that left much of the world's social ills unresolved.

Blaming the East-West struggle for the world's inability to establish justice and end poverty, the pope said misery and suffering remain so great around the globe that the church should consider selling some of its superfluous holdings to alleviate the crying needs of the deprived.

In his most sweeping and detailed social pronouncement since assuming the throne of St. Peter in 1978, the pontiff from Poland criticized both "liberal capitalism and Marxist collectivism" for the injustice and poverty that continue 20 years after Pope Paul VI set out to spur the world to eradicate it.

The strong papal message was contained in a 102-page encyclical entitled "Sollicitudo Rei Socialis," or "Social Concern," that the pope issued to honor and update Paul VI's pace-setting 1967 encyclical on socio-economic development, "Populorum Progressio," or "Progress of Peoples."

While the Roman Catholic Church does not consider papal encyclicals infallible, it treats them as important teachings. Bishops throughout the world are expected to transmit them to their people and apply them to conditions in their own countries.

John Paul said the new encyclical, his seventh, was necessary because conditions in the world today are worse than when Paul VI sought to raise world consciousness to eradicate poverty, injustice and underdevelopment.

"It should be noted that in spite of the praiseworthy efforts made in the last two decades by the more developed or developing nations and the international organizations to find a way out of the situation, or at least a remedy for its symptoms,the pope wrote, the conditions have become notably worse.

"Responsibility for this deterioration is due to various causes," the pontiff continued in his letter, which pulled together virtually all the social themes he has expounded in his world travels in the past decade. "Notable among them are undoubtedly grave instances of omissions on the part of the developing nations themselves and especially on the part of those holding economic and political power."

The main problem, he emphasized, was the world's division into two rival blocs, one practicing "liberal capitalism" and one "inspired by . . . Marxist collectivism." The conflict between these two forces since World War II had emphasized security, arms production and the buildup of dangerous nuclear arsenals, the pope wrote, thereby sapping resources that could be used to eradicate social injustices.

The nuclear arms race, the pope wrote, led to the conclusion that "in today's world, including the world of economics, the prevailing picture is one destined to lead us more quickly toward death rather than one of concern for true development which would lead all toward a more human life."

The pope was as harsh on the West as on the East.

"When the West gives the impression of abandoning itself to forms of growing and selfish isolation, and the East in its turn seems to ignore for questionable reasons its duty to cooperate in the task of alleviating human misery," the pope said, "then we are up against a betrayal of humanity's legitimate expectations -- a betrayal that is a harbinger of unforeseeable consequences -- but also a real desertion of a moral obligation.

"Seen in this way," he said, "the present division of the world is a direct obstacle to the real transformation of the conditions of underdevelopment in the developing and less advanced countries."

The encyclical elaborated on themes that the American bishops have raised in their pastoral letters, condemning nuclear warfare and calling for a more equitable distribution of U.S. economic resources.

The pope urged all people, not just Christians, to work for reforms that would seriously tackle the plight of the underprivileged.

Developing countries, he argued, are not being helped to grow independently but have "become parts of a machine, cogs on a gigantic wheel" that serve the interests of the developed nations.

Blaming many world institutions for perpetuating, if not actually increasing, the gap between rich and poor, the pope called for a rethinking of financial, monetary and trade policies as well as a solution to the Third World's crippling debt.

The pope reminded his bishops that the church, too, could do more to help the poor.

"Faced by cases of need, one cannot ignore them in favor of superfluous church ornaments and costly furnishings for divine worship," the pope wrote. "On the contrary, it could be obligatory to sell these goods in order to provide food, drink, clothing and shelter for those who lack these things.

"For my own part," the pontiff said, "I wish to insist once more on the seriousness and urgency of that teaching, and I ask the Lord to give all Christians the strength to put it faithfully into practice."

The Vatican, which has operated at a deficit in recent years, has never detailed its wealth in art treasures and real estate. Vatican officials have argued that such masterpieces as Michelangelo's "Pieta" are being held in trust for humanity and cannot be sold.

Though Vatican officials later sought to portray the suggestion of selling church properties as more theoretical than practical, there was no doubt that the pope's social message was deeply felt.

"In that document," said France's Cardinal Roger Etchegaray, "all of the pope breathes, body and soul."