Portugal's parliament has passed a bill allowing gay marriage after winning the support of left-wing parties.
The Socialist government's bill won the support of all left-of-centre parties. Right-of-centre parties opposed the change and sought a national referendum on the issue, but their proposal was rejected.
Voting figures were not immediately available but the President of Parliament Jaime Gama announced that the government's bill had passed, as was widely expected.
The proposed law goes to Portugal's conservative President Anibal Cavaco Silva who can ratify or veto. The veto can be overturned by the parliament.
If there is no presidential veto, the first gay marriage ceremonies could take place in April - a month before Pope Benedict XVI is due on an official visit to Portugal.
Its approval would make Portugal the sixth European country to allow same-sex marriages. Gay marriage is currently permitted in Belgium, the Netherlands, Spain, Sweden and Norway.
"This law rights a wrong," Prime Minister Jose Socrates said in a speech to lawmakers, adding that it "simply ends pointless suffering."
The bill removes a reference in the current law to marriage being between two people of different sexes.
"It's a slight change to the law, it's true. But it is a very important and symbolic step towards fully ensuring respect for values that are essential in any democratic, open and tolerant society: the values of freedom, equality and non-discrimination," Socrates said.
He said a referendum was not necessary because the gay marriage proposal was included in the Socialist Party's manifesto in last September's general election, when it was returned to power.
Mr Socrates said the measure is part of his effort to modernise Portugal. Two years ago his government lifted Portugal's ban on abortion.
Like neighboring Spain, which introduced same-sex marriages four years ago, Portugal is an overwhelmingly Roman Catholic country and previous efforts to introduce gay marriage ran into strong resistance from religious groups and conservative lawmakers.
Homosexuality was a crime in Portugal until 1982. In 2001, a law allowed "civil unions" between same-sex couples which granted them certain legal, tax and property rights. However, it did not allow couples to take their partner's name, inherit their possessions nor their state pension, which is permitted in marriages.
A proposal from the Left Bloc and Green Party allowing gay couples to adopt children was voted down Friday. Gay campaigners said they would continue to fight for gay couples' parental rights.
AP