Chilean President Michelle Bachelet has sent legislation to congress seeking to legalise gay marriage, a move that follows a string of social reforms in one of Latin America's most conservative nations.

The bill submitted on Monday would allow gay couples to adopt children and would denote marriage as a "union between two people" rather than between a man and a woman, according to reports.

"We do this with the certainty that it is not ethical nor fair to put artificial limits on love, nor to deny essential rights just because of the sex of those who make up a couple," Bachelet said in La Moneda presidential palace.

In a post on social media, the president wrote: "There are no conditions to love. To keep moving towards an inclusive Chile, today I signed the Equal Marriage bill."

Para amar no hay condiciones. Para seguir avanzando hacia un Chile inclusivo, hoy firmé el proyecto de Ley de #MatrimonioIgualitario. pic.twitter.com/ZARkzOmgOE — Michelle Bachelet (@mbachelet) August 28, 2017

In March, Bachelet, a centre-left politician, pledged to send a full marriage bill to legislators before the end of the year.

But it was not immediately clear if Bachelet would be able to push the gay marriage bill through congress before she leaves office in March 2018.

Though her Nueva Mayoria coalition has a majority in congress, it is severely fractured ahead of elections in November and several members of the coalition hold socially conservative views.

Former President Sebastian Pinera, who hopes to run as the candidate for the conservative opposition coalition Vamos Chile in the November 19 vote, told broadcaster Radio Concierto that marriage is not to be confused with same-sex partnerships.

Pinera, however, said he is against all forms of discrimination and in favour of equal rights for gay couples.

In recent years, Chile has been taking a series of steps on the international stage to promote gender equality.

In 2012, the South American country passed a hate crime and anti-discrimination law that protects individuals harmed on the basis of their sexual orientation or gender identity.

The law was approved following the murder of Daniel Zamudio, a young gay man who died after being severely beaten and had swastikas carved into his body.

Two years ago, Chile's congress had already approved same sex civil unions after years of legislative wrangling. And in 2016, Chile was one of the lead sponsors of a UN Human Rights Council resolution establishing the mandate of an independent expert on sexual orientation and gender identity issues.

Bachelet's push for marriage equality also comes as countries across the region are expanding gay rights.

Same-sex marriage has been legalised in recent years in Argentina, Brazil, Uruguay, and Mexico, despite the powerful influence of the Catholic Church, which opposes such unions.

As of February 1, 2017, there are 21 countries with marriage equality, counting about one billion, or a seventh of the world's population.

Bachelet, who is barred by the current constitution from seeking a consecutive term, has been pushing for legislation opposed by the country's Catholic leadership.

Just last week, Chile's Constitutional Court gave the green light to a law passed in July that will allow abortion in limited cases.

Before that, Chile was one of only a handful of countries in the world that outlawed terminating a pregnancy in any situation, including when a woman's life was in danger.

Bachelet had previously served as president of Chile from 2006 to 2010, during which she also pushed for pay equality legislation and emergency contraception, including to persons under 14.