Turkey has blocked a high-level German delegation from visiting troops at an airbase taking part in the US-led mission against “Islamic State.” The spat appears to be over Germany’s Armenia genocide resolution, reports. 

Turkey has denied permission for a senior German defense official and several members of parliament to visit Incirlik airbase in July, a spokesperson from the German defense ministry said Wednesday, as tensions mount between the NATO allies.

Germany has about 250 troops, six Tornado reconnaissance planes and a refueling aircraft at the airbase in southern Turkey as part of the international coalition fighting the so-called “Islamic State” in Syria.

Ralf Brauksiepe, the undersecretary for defense, planned to visit German troops in July with a parliamentary delegation, but has so far been blocked due to tensions between Berlin and Ankara over a Bundestag resolution earlier this month calling the 1915 massacre of Armenians a genocide.

“The Turkish authorities at the amoment are not approving the travel plans,” a German defense ministry spokesperson said, confirming a report in news magazine “Der Spiegel.”

“There is no written statement on the reason,” he said, adding the delegation still hoped to visit.

“Der Spiegel” reported that permission was denied in retaliation for the Armenian genocide vote.

Ties between Turkey and Germany were already strained before the genocide vote, in particular over President Recep Tayyip Erdogan’s crackdown on the press and human rights abuses tied to ongoing military operations against Kurdish rebels.