European Commissioner Guenther Oettinger has said he did not see the European Union granting Turks visa-free travel this year - as agreed in a migration deal - due to Ankara's crackdown after a failed military coup.
The EU sealed a controversial deal with Turkey in March intended to halt illegal migration flows to Europe in return for financial and political rewards for Ankara.
Nearly 20,000 members of the police, civil service, judiciary and army have been detained or suspended since Friday night's failed coup, in which more than 200 people were killed when a faction of the armed forces tried to seize power.
"The draft law (on ending visa requirements for Turks) is being debated in the European Parliament right now," Oettinger, commissioner for digital economy and society, told several regional German newspapers in an interview published on Tuesday.
"But I predict that we won't have regulation on visa-free travel before the end of the year," said Oettinger, an ally of German Chancellor Angela Merkel, the key driving force behind the migration deal with Turkey.
Turkish President Tayyip Erdogan must address the EU's concerns regarding the principle of the rule of law, he said, adding: "And that's not what it's looking like at the moment."
Oettinger criticised Ankara's recent decision to lift lawmakers' immunity from prosecution, a constitutional change likely to remove a pro-Kurdish opposition party from parliament.
He also slammed the Turkish government for shutting down opposition newspapers and intimidating journalists critical of government policies.
"And it cannot be that judges the government does not like are being removed by the thousands. The independence of the judiciary is a tremendous asset," Oettinger said.
The broad post-coup crackdown and calls to reinstate the death penalty for plotters drew concern from Western allies who said Ankara must uphold the rule of law in the country.
"The death penalty is irreconcilable with our order of values and our treaties. No country can become a member state of the EU if it introduces the death penalty," Oettinger said.
Erdogan has said there could be no delay in using capital punishment after the failed coup attempt, adding the government would discuss it with opposition parties.