Pope John Paul II (search) urged authorities Saturday to stop approving gay marriages, saying they "degrade" the true sense of marriage between a man and a woman.

It was the second time in a week the pontiff has raised the issue, which is making headlines in the United States as gay couples marry in cities like San Francisco and New Paltz, N.Y.

The California Supreme Court (search) on Friday also declined a request to immediately stop San Francisco from marrying gay couples and to nullify the weddings already performed. More than 3,400 gay couples have tied the knot in San Francisco.

John Paul said a family based on marriage between a man and a woman was a pillar of society that justly had rights and duties specific to it.

"This is a time in which there is no lack of attempts to reduce marriage to a mere individual contract, with characteristics very different from those that belong to marriage and the family, and that end up degrading it as if it were a form of accessory association within the social body," he said.

John Paul urged all public authorities, but particularly Catholic ones, to stop approving such laws, saying they should not contribute to legislation contrary to "the primary and essential norms that regulate moral life."

Authorities must instead protect laws that favor the family "knowing that they promote a social development that is just, stable and promising," he said.

The pope made the comments as the new ambassador of Argentina to the Holy See (search) presented his credentials. In 2002, the city of Buenos Aires passed a law extending certain civil rights like health insurance and pension rights to same-sex couples — the first Latin American city to adopt such a measure.

Last year, the Vatican launched a global campaign against gay marriages in a bid to stem the tide of widening legal recognition for same-sex unions in Europe, North America and elsewhere.

John Paul has pressed his point on several occasions since then. On Thursday, he called for the support of the "authentic" Christian family, which he defined as being based on marriage between a man and a woman.

The debate has spilled into the U.S. presidential race, with President Bush saying this week he would back a federal constitutional amendment barring such marriages.