Turkey cannot revive its strained relationship with the European Union until it frees German citizens it has detained, Germany’s foreign minister said on Friday as his Turkish counterpart called for a fresh start with the bloc.

Turkey, which has had awkward relations with Europe for several years, is seeking to mend them at a time when its currency has been falling and its ties with the United States have sharply deteriorated.

Germany says 50 of its citizens are being held in Turkish prisons following a crackdown after a failed coup in July 2016. Only seven have been charged. Another 35 are blocked from leaving the country.

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“These cases must be resolved,” Foreign Minister Heiko Maas, who will make his first official trip to Ankara next week, told reporters during a meeting between EU foreign ministers and countries aspiring to join the European Union, including Turkey.

“That would be a step toward normalizing relations with Germany, but also with the European Union,” he said, adding that he would press the issue during his two-day trip to Ankara and Istanbul from Wednesday.

Ties between Germany and Turkey, both members of the U.S.-led NATO alliance, have been extremely tense since Berlin condemned Ankara’s arrests of some 50,000 people and the suspension or firing of 150,000 in the post-coup crackdown.

There has however been a slight thaw in recent months after Turkey released one German-Turkish journalist and allowed another German citizen to leave the country.

Talks with Turkey on EU membership were effectively suspended last year, although Ankara remains a candidate.

Ankara says the scale of its crackdown is justified by the gravity of events on July 15, 2016, when rogue soldiers commandeered tanks, planes and helicopters, bombing parliament and government buildings in their attempt to seize power.

Turkish Foreign Minister Mevlut Cavusoglu said in Vienna that the EU failed to understand Turkey’s security challenge.

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“We don’t have any problem with the EU or with Europe, we are part of this continent,” Cavusoglu told reporters. “Yes we have some issues with the European Union, particularly after the attempted coup. The measures we had to take were not understood by Europe ... but now we want to normalize our relations.”

As well as reviving stalled EU membership talks, Ankara wants more EU money to house Syrian refugees, a deeper customs union with the bloc and progress in talks on letting Turks visit the EU without visas.

The EU is wary of what it sees as rapid backsliding on democracy and human rights in Turkey, and was angered by rhetoric from President Tayyip Erdogan last year, including comparing the Dutch and German governments to Nazis.

Asked in Vienna if Turkey needed economic aid from the European Union to stop the fall in the value of the Turkish lira, Maas said: “The first thing for Turkey is to complete the conditions for normalization ... the ball is in Turkey’s court.”