Thousands of Portuguese poured onto the streets of Lisbon Sunday in protest of a gay marriage law currently seeking the president's approval, the Spanish news agency EFE reported.

Organizers estimated the event, called β€œin defense of the family,” attracted a crowd of 5,000, but no official figures were reported.

Demonstrators marched down Lisbon's main downtown artery Av. da Liberdade (Liberty Avenue) calling on President Anibal Cavaco Silva to reject a gay marriage law approved twice by lawmakers. Silva is a Roman Catholic and a member of the PSD party, groups which oppose the legalization of gay marriage, and he has publicly stated his opposition to gay marriage. However, Silva has several options before him, including vetoing the bill. Commentators in the Portuguese press have speculated he could forward the issue to the Constitutional Court. Last year, despite the fact that Portugal's Constitution outlaws discrimination based on sexual orientation, the court denied a lesbian couple the right to marry in a narrow 3-to-2 decision. The ruling prompted Socialists to draft the gay marriage bill.

Protesters are also demanding a referendum on gay marriage, although Parliamentarians have already rejected such a measure.

Portugal's Parliament approved the bill on February 11 and forwarded it to the president. Under the bill, gay and lesbian couples would be allowed to marry but not adopt children.

Cavaco Silva has a week left to decide what to do with the bill. Supporters, however, say a veto would only delay the legislation. The Socialist-controlled Parliament, led by Prime Minister Jose Socrates, is prepared to overturn a presidential veto.

The Vatican condemned the legalization of gay marriage in neighboring Spain in 2005 and has called for the ouster of Socialists in the country, but the church's opposition in Portugal has been muted. However, Pope Benedict is widely expected to criticize the bill when he visits Portugal in May.

Gay marriage is legal in five European counties, including Spain, Belgium, the Netherlands, Norway and, most recently, Sweden.