SANTIAGO, Chile -- Chilean President Michelle Bachelet introduced a bill Monday to legalize gay marriage, the latest in a series of recent reforms in a country long regarded as one of Latin America's most socially conservative.

Bachelet signed the proposal, which will be sent to lawmakers, at a ceremony in the presidential palace. She said the measure seeks to expand the definition of marriage between a man and a woman and would also expand rights for gay couples, allowing them to adopt children.

"We can't let old prejudices be stronger than love," Bachelet said.

Chile approved civil unions for same-sex couples in 2015 and decriminalized gay sex in 1999. The bill comes a week after Chile's constitutional Court upheld a measure that would end the country's absolute ban on abortions.

Civil unions have been recognized in several South American countries, though only Argentina and Uruguay have codified same-sex marriage. Gay marriage has also been legalized in Colombia under a ruling by that nation's Supreme Court.

It's unlikely Bachelet will be able to push the measure through Congress before she ends her term in March 2018. But gay right advocates celebrated the decision as an important step toward full rights.

"It's the beginning of the end of discrimination based on sexual orientation to access marriage," said Luis Larrain, founder of the Iguales Foundation.

"This day will be remembered as much as the day when women were granted the right to vote, slaves were freed or children born out of wedlock were granted the same rights."