BERLIN (Reuters) - German lawmakers canceled a visit to Turkey where they had planned to talk to opposition lawmakers, governors and rights groups about last month’s referendum, saying Ankara had refused to give them a security detail.

Claudia Roth, a Green Party lawmaker and vice president of the Bundestag (German lower house), said on Wednesday Turkish officials had informed her the German delegation would have neither access to parliament in Ankara nor security guards.

The visit’s cancellation is likely to further strain relations between the two NATO allies that have deteriorated over Turkey’s refusal to allow German parliamentarians access to troops based at the Incirlik air base.

“Yesterday we received the information that the highest level on the Turkish side considers that at the moment it is not suitable for German members of parliament to conduct political discussions in Turkey,” Roth said.

“This is de facto a rejection of political dialogue. It is a red card for the German parliament.”

A Turkish Foreign Ministry spokesman said: “At this stage, it was thought that it would be better if this visit did not take place, and the demanded meetings were not scheduled for this reason.” The spokesman declined to comment why it would be better to cancel the visit.

Turkey has refused permission for German lawmakers to visit Incirlik, where roughly 250 German soldiers are stationed as part of the coalition against Islamic State militants.

Defence Minister Ursula von der Leyen has said she is looking for an alternative base for the troops and that Jordan is an option.

The parliamentary delegation headed by Roth had also wanted to meet the governor of Diyarbakir, the main city in Turkey’s mainly Kurdish southeast.

Relations between the two countries soured in the run-up to Turkey’s April 16 referendum that approved an increase in President Tayyip Erdogan’s powers, which alarmed Western allies concerned about a drift towards authoritarian rule in Ankara.

Erdogan angered German and European officials by accusing Germany of “Nazi-like” tactics after some local authorities, citing safety concerns, canceled rallies of expatriate Turks to be attended by Turkish ministers to campaign for the referendum.