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It comes after Turkey refused to allow German politicians to visit soldiers at Incirlik air base. The German Chancellor said today: "This is unfortunate, and we have made this clear through various channels. "We will continue to talk with Turkey, but in parallel we will have to explore other ways of fulfilling our mandate."

GETTY Angela Merkel is not pulling any punches when it comes to German-Turkish relations

More than 250 German soldiers are stationed at the base, contributing to NATO's mission targeting Islamist State militants in neighbouring Syria. The military personnel fly Tornado surveillance missions over the wartorn country, and refuel flights for partner nations battling ISIS extremists. Turkish foreign ministry sources told Reuters that a visit by German parliamentarians "would not be appropriate at this time". Turkey similarly refused access to German authorities late last year, although that visit eventually went ahead. Speaking to reporters, Angela Merkel said: "We will continue to talk with Turkey, but in parallel we will have to explore other ways of fulfilling our mandate. "That means looking at alternatives to Incirlik, and one alternative among others is Jordan."

For historic reasons and as part of efforts to prevent abuse of power, the Bundeswehr army is controlled by the German parliament - not the government - meaning lawmakers have the right to inspect its activities, with the country and abroad. A spokesman for the German foreign minister said it was "completely unacceptable" for Turkey to keep members of the parliamentary defence committee from visiting their own soldiers. Foreign Minister Sigmar Gabriel is expected to raise the issue with colleagues from other NATO governments in Washington on Tuesday.

A look back on the shocking Turkish military coup that left 294 dead Wed, July 27, 2016 The violent military coup to overthrow Turkey's President Erdogan has 'failed' leaving at least 104 dead and more than 1,500 wounded Play slideshow Getty Images 1 of 42 A police officer talks with the soldiers involved in the coup attempt after they surrendered

Relations between Ankara and Berlin deteriorated sharply in the run-up to an April 16 referendum in Turkey - which saw President Tayyip Erdogan's powers dramatically increase. Citing public safety concerns, Germany banned Turkish politicians from addressing rallies of expatriate Turks, prompting Erdogan to accuse Berlin of "Nazi-like" tactics. Only a narrow majority of Turks had backed changing the constitution which grant Mr Erdogan sweeping executive powers. Germany and other Western allies have voiced concern about what they fear is a drift towards authoritarian rule in Turkey.

GETTY German Chancellor Angela Merkel has been speaking to reporters

More recently, Berlin angered Ankara by granting asylum to some Turkish holders of diplomatic passports. According to reports in German media, more than 400 Turkish military personnel, diplomats, judges and other officials - along with their relatives - had sought political asylum in Germany. They fear being caught up in Turkey's crackdown against those Mr Erdogan blames for last year's failed coup attempt - namely supporters of Fethullah Gulen, a reclusive US-based Islamic preacher who has denied the charges against him. Turkish authorities have detained tens of thousands of officials on suspicion of involvement. The vast crackdown heightened tensions between Turkey and Germany, which is home to a three-million-strong ethnic Turkish population, the legacy of a massive "guest worker" program in the 1960s and 1970s.

GETTY The recent Turkish referendum granted President Erdogan sweeping powers