NATO chief Jens Stoltenberg contacted each of the German and Turkish foreign ministers last week in an attempt to resolve the dispute over Turkish airbases.
The dispute centers over visits by German officials and lawmakers to Turkish airbases, which is part of a wider row between the two allies.
“We hope that Germany and Turkey are able to find a mutually acceptable date for a visit,” a NATO spokesman said.
Stoltenberg had called Sigmar Gabriel and Mevlut Cavusoglu on Friday to ask them to settle the disputes.
Germany has refused to extradite asylum seekers Turkey says were involved in last year’s coup attempt, Berlin is demanding the release of a Turkish-German journalist and Ankara has refused to let German lawmakers visit soldiers at two airbases.
German soldiers contribute to a NATO air surveillance mission at Konya, 250 km (155 miles) south of the Turkish capital Ankara, and its troops stationed at another air base, in Incirlik, have already been moved to Jordan.
Germany’s armed forces are under parliamentary control and Berlin says the lawmakers must have access to its soldiers.
On Friday, Berlin said that Ankara once again blocked a visit by its lawmakers to German troops stationed at Konya.
Turkey asked the legislators to postpone a scheduled visit next Monday, the German foreign ministry said, adding that it regretted the decision.
The dispute comes after Germany last month pulled out 260 troops from Turkey’s Incirlik base, from where a multinational coalition is fighting the ISIS terror group, and redeployed them and their Tornado surveillance jets to Jordan.
Some 20-30 German troops have remained at Konya as part of an Airborne Warning and Control System (AWACs) mission, part of the coalition’s campaign against ISIS in neighboring Syria and Iraq.
The German foreign ministry insisted that all sides, including NATO, remained in talks on setting a new date for a visit.
Lawmaker Wolfgang Hellmich, head of the parliamentary defense committee, said Turkey’s latest move amounted to another denial of the right to visit German troops, and that Ankara had referred to the “strained bilateral relations”.
Hellmich added that he saw no chance now of parliament renewing the mandate for the smaller contingent later this year.