This was stated by NATO Secretary-General Jens Stoltenberg on Tuesday ahead of a meeting with EU defense ministers in Brussels, Censor.NET reports citing Reuters.
"We will never respect or accept the violation of the territorial integrity and sovereignty of Ukraine," he stated.
Stoltenberg added that the Alliance continues a dialogue with Russia and is looking forward to a meeting in the near future.
The statement came as a note of caution a day after U.S. President-Elect Donald Trump agreed to boost cooperation with Russian President Vladimir Putin.
The presidents did not discuss the Crimean and Donbas issues, Dmitry Peskov, the spokesperson for the Russian president, said on Tuesday.
Stoltenberg's message was echoed by German Defense Minister Ursula von der Leyen, who said she was also concerned about Russia's military activities in eastern Ukraine and Syria.
"It is important not to forget our principles," she said, stressing that Crimea's annexation remained "an open point."