German Chancellor Angela Merkel has pledged to stop Turkey becoming a member of the European Union, in a television debate with her main political rival Martin Schulz.
Mrs Merkel, who is seeking a fourth term as German leader, said if re-elected, she would convince other European leaders to end negotiations with Turkey to join the bloc.
"The fact is clear that Turkey should not become a member of the EU," the Christian Democratic Union party leader said.
Turkey began accession talks to join the EU in 2005, however, talks have halted amid criticism of President Recep Tayyip Erdogan's crackdown on political opponents.
During the debate on Sunday evening, Mrs Merkel appeared to shift her position on the issue after Social Democrat (SPD) leader Mr Schulz promised to end the accession negotiations.
"If I become German chancellor, if the people of this country give me a mandate, then I will propose to the European Council that we end the membership talks with Turkey," Mr Schulz said.
"Whether we can win over all the countries for this I don't know. But I will fight for this."
The centre-right chancellor warned against the move at a time when 12 German citizens are being held in the country on political charges.
"I do not intend to break off diplomatic relations with Turkey just because we're in an election campaign and want to show each other who is tougher," she said.
However, Mrs Merkel returned to the issue later on in the debate, making a u-turn by promising to end the negotiations.
The CDU has consistently opposed Turkish membership of the EU, although negotiations began shortly before Mrs Merkel was elected to power. She has previously said she would respect the talks.