Juncker charged that "Turkey is withdrawing from Europe by giant steps," adding that it was up to President Recep Tayyip Erdogan...
And in Berlin, German Chancellor Angela Merkel warned there could be no progress even in trade relations with Turkey while the rule of law was not guaranteed there.
Juncker charged that "Turkey is withdrawing from Europe by giant steps," adding that it was up to President Recep Tayyip Erdogan to officially call an end Turkey's efforts to join the EU.
Juncker said he suspected that Erdogan was hoping that Europe would be the one to break off the talks "in order to blame the European Union" for their failure.
But the bloc must avoid "falling into the trap" as the "responsibility is entirely on the Turkish side," he told an annual conference of EU ambassadors in Brussels.
"The question is to know if we must put an end to the negotiations -- which is a purely theoretical question as there are no negotiations."
Relations with Turkey, and especially between Berlin and Ankara, have hit rock bottom in recent months, stoking calls for Ankara's EU accession talks to be suspended.
Turkey began formal membership talks in 2005 after years of foot-dragging by some EU member states such as France who were wary of admitting a large Muslim country.
But progress has been slow and the negotiations came to a virtual halt last year after Erdogan began a massive crackdown following an attempted coup in July, sending ties plunging to a new low.
Immediately after the failed coup, Turkey imposed a state of emergency under which more than 50,000 people have been arrested and almost three times that number have lost their jobs, including teachers, judges, soldiers and police officers.
In December, EU member states agreed that no new accession chapters would be opened until Ankara reversed course.
Merkel, at a Berlin press conference, said about Ankara ties that "I would very much like having better relations, but we have to face reality".
Under current conditions, she also said she did not see how the EU and Turkey could hold talks on expanding their customs union.
Good ties are "linked to respect for the rule of law, and this isn't guaranteed right now in Turkey".
"Therefore it's a very complicated phase of our relations."
She reiterated Germany's demand that Turkey free from custody several journalists and rights workers, including Die Welt daily correspondent Deniz Yucel.
"Our demand is very clear -- that the people who have been arrested there are released."