The Greek parliament will vote later this month on granting same-sex couples the right to a civil union, despite strong opposition from the influential Orthodox church.
The Greek government is seeking to meet its obligations after it was condemned for anti-gay discrimination by the European Court of Human Rights in 2013.
Legislators will consider a draft law on December 22 that will include gay couples in a 2008 civil unions law from which they had been explicitly excluded.
The governing coalition of the left-wing Syriza party and the nationalist Independent Greeks (ANEL) enjoy a majority in the 300-seat parliament, but ANEL has made it clear that it intends to vote against the motion.
Greek Prime Minister Alexis Tsipras hopes support from the socialist and centrist opposition will see the bill safely through parliament.
Greece is one of the last European countries where same-sex couples cannot receive some kind of official recognition for their relationship.
The country's first two same-sex civil marriages held in 2008 were annulled by a court a year later under pressure from the Greek Orthodox Church, which officially frowns upon same-sex relations.
Lobbying by the church was also instrumental in excluding same-sex couples from benefiting from the 2008 civil union bill, which modernised family law and aligned national law with EU rules.