Mexico's President, Enrique Pena Nieto, has proposed constitutional reform to legalise same-sex marriage across the country.
The decision follows a Supreme Court ruling that opened the way to such unions.
Gay marriage is only legal in the capital, Mexico City, and a few states.
Elsewhere in Latin America, Argentina, Brazil, Uruguay and most recently Colombia have already legalised same-sex marriage.
Mexico's Supreme Court declared last year that it was unconstitutional for the country's states to ban such marriages.
Mr Pena Nieto made the announcement at an event marking Mexico's national day against homophobia.
On Twitter, the president said: "For an inclusive Mexico that recognises in diversity one of its biggest strengths." He used a hashtag in Spanish saying: "Without homophobia".
His and the Mexican government's profile pictures on Twitter were overlaid with the rainbow flag of gay pride.
Argentina was the first Latin American country to legalise same-sex marriages in July 2010.
The BBC's Will Grant in Mexico City says the governing PRI party has always prided itself on upholding the conservative values of Mexican society.
But the move is perhaps a recognition by the Pena Nieto government that attitudes towards gay rights have relaxed in recent years, our correspondent adds.