VATICAN CITY -- Pope John Paul II, pressing on with his quest to bring his often unruly Latin American flock in line, has warned religious orders there to steer clear of leftist ideologies and embrace Vatican policy "with a pure and undivided heart."

A 46-page papal letter, which was issued Thursday and emphasized "the urgency of a new evangelization in Latin America," was timed to coincide with the 500th anniversary of the spreading of the Catholic faith to the western hemisphere.

The letter addressed the increasing tension between Rome and Latin America's multiple religious orders -- and the nuns, monks and priests who belong to them -- over the interpretation of religious duties, Vatican officials said.

The letter, released in Spanish and Portuguese, also followed by several weeks the release of a strongly worded Vatican document that ordered Roman Catholic theologians around the world to conform to the Vatican line, asserting that, "The freedom of the act of faith cannot justify a right to dissent."

Although the first document -- expressly approved by the pope -- was the product of several years' work and this week's papal letter was a spontaneous reaction to an emerging situation, a senior Vatican source allowed that both documents were part of an effort by the pope to bring "certain {dissenting} elements to heel."

The letter reflects "a built-in tension" between the church hierarchy, including local bishops, and the more charismatic nature of the religious orders, said the Vatican source, who requested anonymity.

Although the religious orders often have been the inspiration for changes, in Latin America they have also been associated with deviation from the central church line, the source said.

In Nicaragua in recent years, for example, there were strong frictions between the Catholic hierarchy and the so-called people's church inspired by liberation theology. The leftist Latin American-born movement, anathema to the pope, emphasizes the social role of the church in a manner that Vatican hardliners interpret as dangerously close to Marxism.

In perhaps the most famous clash between the Vatican and a proponent of liberation theology in Brazil, the left-leaning Rev. Leonardo Boff was ordered by Rome to a penitent term of silence after he outraged the pope with his criticism of what he termed Vatican authoritarianism.

In his most recent letter, Pope John Paul II expressed sympathy and praise for members of religious orders in their struggle to help the poor on a continent where the socio-economic conditions "are a reason for tremendous worry."

But he also noted two Vatican documents on liberation theology issued in 1984 and 1986, which he called prophetic in "unmasking the failed ideological utopias and political servilism."

Religious life should be "grounded in theological virtue, because faith doesn't cede to the mirage of ideologies {and} Christian hope shouldn't be confused with utopian thinking," he wrote.

Making a clear reference to the notion of armed struggle, which was accepted by some fringe elements of the liberation theology movement, he counseled love in the face of enemies, "never succumbing to the temptation of violence."

Acknowledging that priests and other members of religious orders had become involved in political activity, the pontiff lamented "those cases in which the church's orientation toward the poor led to a politicization of the consecrated life, not free of {political} parties and violence, with the exploitation of religious people and institutions."

The pontiff sounded anew his call for obedience, an apparent response to recent frictions between Vatican-appointed bishops and local groups representing religious orders in Latin America, the Vatican official said.

Concluded the pope: "In truth, one is not authentically living the life of poverty if not fully living chastity and obedience; . . . nor is one obedient to the design of the father who does not embrace, with a pure and undivided heart, the detachment from earthly things."