European Union and Turkish flags fly outside a hotel in Istanbul, Turkey May 4, 2016. REUTERS/Murad Sezer

Austria's foreign minister has threatened to block the expansion of negotiations with Turkey on its accession to the European Union, which could scupper a landmark migration deal between Brussels and Ankara.

Foreign Minister Sebastian Kurz's comments, published on Sunday, risk exacerbating a row between Austria and Turkey that flared last week when Austrian Chancellor Christian Kern suggested ending Turkey's EU membership talks altogether because of the country's democratic and economic deficits.

Talks on Turkish accession have made only slow progress since they began in 2005, with just one "chapter" concluded of 35 such policy areas where Turkey must adopt and implement EU rules.

"I have a seat and a vote in the (EU) foreign ministers' council. There the question is whether new negotiation chapters will be opened with Turkey, and I am against it," Kurz said in an interview with Austrian daily Kurier, threatening to block the unanimous agreement required.

The Turkish government's crackdown on followers of a U.S.-based cleric whom it blames for last month's failed coup has strained relations with the 28-nation bloc, which depends on Ankara to restrict the westward flow of migrants.

Turkey has so far lived up to its side of the deal with Brussels to stop illegal migration to Europe via its territory, in return for financial aid, the promise of visa-free travel to much of the bloc and accelerated talks on membership.

Visa-free access has been subject to delays however, due to a dispute over Turkish anti-terrorism legislation, which some in Europe see as too broad, and the post-coup crackdown. Kurz said Turkey had not met the conditions for progress to be made.

"The criteria for visa liberalization will not be fulfilled by Turkey. And the requirements for accession talks have not been met," Kurz said.

German Foreign Minister Frank-Walter Steinmeier said on Friday accession talks were "as good as deadlocked" but he rejected calls to halt them entirely, saying the bloc needed to think more broadly about how to frame its ties with Ankara.

Austria's centrist coalition government is under pressure from the resurgent anti-immigration Freedom Party, which is running first in opinion polls with support of more than 30 percent and is vehemently opposed to Turkish EU accession.

Kern's Social Democrats and Kurz's conservative People's Party must either work together or face a snap parliamentary election, and Kurz is widely seen as likely to take over as leader of his party before then.

"Turkey has for its part already declared that it does not want to fulfill all the criteria. As a result the migration deal will not last," Kurz told tabloid newspaper Oesterreich.