Jean-Claude Juncker said Thursday's vote by the European Parliament to suspend talks with Ankara should not be underestimated because, although not binding, "it will produce effects in the capitals" of EU states that decide on membership.
Speaking to Belgian newspaper La Libre Belgique, Juncker also dismissed President Tayyip Erdogan's threats to end a refugee deal with the EU that has sharply reduced the flow of migrants to Europe from the Middle East and Asia, according to Reuters.
He urged Erdogan to carry out the necessary reforms, starting with an overhaul of anti-terrorism legislation, if he wants Turkish citizens to get visa-free travel to the EU -- a concession that is part of the refugee deal.
Juncker also denied having said he would quit if Martin Schulz left his job as president of the European Parliament, dismissing media reports more strongly than in previous statements.
Schulz, a German center-left politician, decided this week not to seek a new mandate, a move that is likely to alter the EU's political balance.
A shift in favor of Europe's center-right could raise questions about Juncker's staying in his post and on Donald Tusk's presidency of the European Council of EU governments.
"According to legal texts, I am in charge until the first of November 2019," Juncker said.
In new sour remarks against U.S. president-elect Donald Trump, Juncker stressed the Democratic candidate Hillary Clinton got more votes than him, although she lost the elections. Earlier this month, Juncker said Trump was ignorant of Europe and his election posed a risk to EU-U.S. relations.
Trump's threats to reduce the U.S. engagement toward European security should be used by the European Union to strengthen its common defense policy, Juncker said, adding that Trump is repeating warnings already raised by his predecessors.
Next week the European Commission will present an "action plan" on European defense, Juncker said.