BERLIN (Reuters) - German politicians visited their country’s troops at an air base in Turkey on Friday but some lawmakers said they would not extend the airmen’s mission to take part in NATO air patrols unless an underlying dispute over visiting rights was resolved.

Germany’s armed forces are under parliamentary control and Berlin insists lawmakers must have access to them, but Turkey has repeatedly prevented visits from taking place. Friday’s visit was arranged by NATO, sidestepping Ankara’s objections.

Some of the lawmakers, who were flown to the Konya air base on a NATO plane from the alliance’s Brussels headquarters, said Germany’s parliament would only extend the troops’ mandate if future visits were more straightforward. The current mandate expires at the end of this year.

“The conflict over visiting rights must be dealt with before parliament votes again on the mandate,” said Green lawmaker Tobias Lindner, a member of the delegation. “Flying via Brussels cannot be a long-term solution.”

Relations between Ankara and Berlin were already strained by Turkish President Tayyip Erdogan’s crackdown on opponents after a failed coup last year, and Turkey’s refusal to let German members of parliament visit airmen based in the country has exacerbated tensions.

“It must be possible for us to visit our soldiers serving abroad,” said Henning Otte, a lawmaker for Chancellor Angela Merkel’s ruling conservative party. “Germany has a parliamentary army.”

Seven German lawmakers visited the handful of German troops serving in a NATO air surveillance mission at Konya. The delegation was led by NATO’s Deputy Secretary General Rose Gottemoeller.

There are usually around 25 German soldiers based in Konya although only a handful were present at the base on Friday. Some more arrived with the lawmakers in the NATO plane.

Turkey had objected particularly strenuously to the participation of a member of Germany’s far-left Left party whom Ankara accuses of supporting terrorists.

Repeated refusals by Ankara to let lawmakers visit German soldiers at Incirlik, another base in Turkey, prompted Berlin to relocate those troops to Jordan in July.

Turkey and Germany are also at odds over Berlin’s refusal to extradite asylum seekers Ankara accuses of involvement in last year’s failed coup against Erdogan, while Berlin is demanding the release of an imprisoned Turkish-German journalist.

The deterioration in relations has led German Chancellor Angela Merkel to say she will seek to end Turkey’s membership talks with the European Union.