Updated

The Vatican took aim Thursday at Roman Catholic politicians, telling them church teaching demands they defend "the basic right to life from conception to natural death."

A new set of guidelines approved by Pope John Paul II for Catholic politicians said church opposition to abortion, euthanasia and same-sex marriage was not up for negotiation.

Their release comes a week before major demonstrations planned in the United States by abortion rights and anti-abortion groups and amid continuing efforts, mainly in Europe, to legalize euthanasia and gay marriages.

The Vatican said it was publishing the document now because of medical and scientific advances and because of the "emergence of ambiguities or questionable positions in recent times."

The guidelines, prepared by the Vatican's orthodoxy watchdog, the Congregation for the Doctrine of the Faith, make no changes to the church's long-held positions.

Rather, they serve as a reminder to Catholic politicians of church teachings, so that when they vote for legislation or otherwise influence public policy, they do so in line with the church's "nonnegotiable ethical principles."

In particular, the document said laws concerning abortion and euthanasia "must defend the basic right to life from conception to natural death. In the same way, it is necessary to recall the duty to respect and protect the rights of the human embryo."

It said laws safeguarding marriage between man and woman must be promoted and that "in no way can other forms of cohabitation be placed on the same level as marriage, nor can they receive legal recognition as such."

The document also referred vaguely to issues of peace, saying Catholics should not confuse the church's promotion of peace and rejection of violence with "secular" pacifist and ideological visions. The pope's opposition to war in Iraq is likely to make him a rallying point in the event hostilities erupt.

"The church recognizes that while democracy is the best expression of the direct participation of citizens in political choices, it succeeds only to the extent that it is based on a correct understanding of the human person," the document said. "Catholic involvement in political life cannot compromise on this principle."

The guidelines don't mention punishment -- such as excommunication -- for Catholic politicians who fail to toe the line. Rather, they frame the issue as one of "conscience."

"Scientific progress has resulted in advances that are unsettling for the consciences of men and women, and call for solutions that respect ethical principles in a coherent and fundamental way," the document said.

"Catholics, in this difficult situation, have the right and the duty to recall society to a deeper understanding of human life and to the responsibility of everyone in this regard," it said.

The Vatican stressed it wasn't trying to dictate policy or interfere in matters of state, but to "instruct and illuminate" Catholic political leaders.

And it challenged the idea that ethical pluralism "is the very condition for democracy."

The document was released a week before the 30th anniversary of the U.S. Supreme Court's Roe v. Wade decision legalizing abortion. Demonstrations by abortion rights and anti-abortion groups are planned for next Wednesday.

The Vatican never disguised its irritation with Geraldine Ferraro, a Catholic and the U.S. Democratic vice presidential candidate in 1984, for her position that she opposed abortion but also opposed outlawing it.

Recently, former Italian Premier Giulio Andreotti, a practicing Catholic, said he deeply regretted having signed the law legalizing abortion in Italy when he was prime minister in 1978.

The Vatican has also been campaigning against efforts to legalize same-sex marriages and offer the unions the same benefits granted traditional heterosexual marriages.

Bishop Wilton Gregory, president of the U.S. Conference of Catholic Bishops, welcomed the publication of the document, saying it "addresses some of the profound challenges faced by Catholic politicians and voters who are confronted with various moral and social issues in the context of a democratic society."

He said he hoped the document would encourage U.S. Catholic politicians to continue to "respect the most essential moral values of our human nature." The Vatican released similar statements from German and Italian cardinals along with the document on Thursday.

While not offering concrete examples of legislation for Catholic politicians to promote, the document proposed a model for them to emulate: St. Thomas More, the 16th-century lawyer and diplomat who refused to renounce the pope and recognize the king as head of the English church.

King Henry VIII had More beheaded for his positions. Two years ago, Pope John Paul II made More the patron saint for politicians.

"He taught by his life and his death that 'man cannot be separated from God, nor politics from morality,"' the document said.