"The red line was crossed. That is why I am very happy about the clarification from NATO Secretary General Jens Stoltenberg that NATO will not send troops to Ukraine," Tanner said on Saturday in an interview with Austrian newspaper Die Presse.
The comment came after recent decisions by the US and some of its allies to allow Ukraine to use US- or Europe-supplied weapons to strike targets across the internationally recognized borders of Russia for counter-fire purposes. Western countries have also been discussing sending troops or military instructors to Ukraine.
Western countries have been providing massive military and financial aid to Kiev since the start of Russia's military operation in Ukraine in February 2022. The Kremlin has consistently warned against continued arms deliveries to Kiev, saying it will lead to an escalation of the conflict.