Turkey plans to keep holding rallies in Germany and the Netherlands to convince Turks staying the two countries to back President Tayyip Erdogan's plan to widen his powers.
This despite both the countries concerned about the expansion of presidential power in Turkey.
Foreign minister Mevlut Cavusoglu said authorities in the two countries do not have the right to impose restrictions on these rallies.
He said they would be held in the run-up to the April 16 referendum.
"None of you can prevent us," he told a campaign event in southern Turkey. "We can go anywhere we want, meet our citizens, hold our meetings."
The defiant Turkish comments highlight the import Erdogan places on securing the new powers, especially since a failed military coup last July, in what could turn out to be a close vote.
The disagreement has led to sharp exchanges between the NATO partners. Adding to the tensions, Germany has demanded the release of a German journalist arrested in Turkey on Monday, while Erdogan on Friday called him a "German agent."
Chancellor Angela Merkel spoke by phone on Saturday with Turkish Prime Minister Binali Yildirim, a German government spokesman said, without providing details of the conversation. The two countries' foreign ministers are due to meet in Berlin on Thursday.
Several members of Merkel's coalition voiced concerns on Saturday about Turkish politicians rallying support among Germany's 1.5 million Turkish citizens.
Juergen Hardt, foreign policy spokesman for her conservative Christian Democratic Union, told Reuters: "We don't want marketing for the undemocratic and illegitimate Turkish referendum on German soil."
Several events have already been blocked for security reasons, sparking anger among Turkish leaders who accused Germany of a double standard.
Turkish Economy Minister Nihat Zeybekci has had two events cancelled, but plans to speak at events on Sunday in Leverkusen and Cologne in the state of North Rhine-Westphalia, which has a large Turkish population.
Critics of Erdogan fear the proposed new powers, including freedoms to govern by executive orders, would entrench autocratic trends. Erdogan says they are vital in tackling Kurdish rebels, Islamist militants and other political enemies in a land with a history of unstable coalition governments.
The Dutch government said on Friday it would inform Ankara of its opposition to "undesirable" proposals to hold a referendum rally in Rotterdam.
"The Netherlands told us 'You can’t campaign in our public spaces'. What do you mean, we can't? Where is democracy... where is freedom of expression?" Cavusoglu said.