Germany's Social Democrats are pushing for a vote this week to legalise gay marriage, spring boarding off a surprise shift from conservative Chancellor Angela Merkel three months before an election.
The issue is now a crucial election topic, after Ms Merkel's three potential coalition partners made it a condition for sharing power.
At an event on Tuesday evening (NZT), Ms Merkel said she had taken note of other German parties favouring same-sex marriage and would allow a free vote.
"I would like to lead the discussion more into a situation where it is a question of conscience rather than something I push through with a majority vote," she said.
The move could antagonise some in her traditionally Catholic conservative bloc, some of whom oppose any change. Ms Merkel has previously argued against same-sex marriage.
Leader of the Social Democrats, Martin Schulz, said his party would push for a vote in parliament this week.
Mr Schulz said he "hoped their colleagues in the conservatives would cooperate", raising pressure on his conservative partners who want a vote after the election.
Mr Schulz needs to make up ground for his centre-left party in the election race and has sharpened his attacks on Ms Merkel, but he made clear he would not end the coalition.
Ms Merkel's conservatives accused him of acting irresponsibly.
With broad support among Germans for gay marriage, the law would likely get approval in the lower house of parliament if conservatives could vote according to their conscience and not face a party whip.