Pope Benedict has called on Portuguese Roman Catholics to oppose gay marriage as the nation's president prepares to decide whether to veto a gay marriage bill approved by lawmakers or allow it to come into force, Reuters reported.

Speaking Thursday in the city of Fatima, the pope called for a greater defense of what he said were “essential and primary values of life,” among which he included the family. He said the family was “founded on indissoluble marriage between man and woman.”

Abortion – legal in Portugal since 2007 – and gay marriage were “among some of the most insidious and dangerous challenges facing the common good today.”

The pope has been warmly greeted during his visit to the Catholic stronghold of Portugal. Up to half a million people showed up to hear the 83-year-old pontiff speak at one of holiest shrines where the Church believes the Madonna appeared to three poor shepherd children in 1917.

President Anibal Cavaco Silva is under pressure by the Church and conservative groups to reject the gay marriage bill approved in February by lawmakers. Yet he has denied reports that he's decided to veto the bill soon after the pope's arrival.

In March, the president, a Catholic, forwarded four out of five of the bill's articles to the Constitutional Court, setting aside a measure that prohibits gay adoption. He said he did so because he doubted the bill's constitutionality, but refused to say why he did not include the article on adoption.

The court's majority, however, ruled the four articles to be constitutional. By law, Cavaco Silva has 20 days from April 28 to make his decision.

Social Democrats – led by Prime Minister Jose Socrates – say they have the votes to override a veto.

If the bill is approved, Portugal would join five European countries – Spain, Belgium, the Netherlands, Norway and, most recently, Sweden – in legalizing gay marriage.

Lawmakers in Argentina and Iceland are also considering legalizing gay marriage.