The war in Ukraine is the most dangerous moment for Europe since World War Two, and Russia must not be allowed to win, NATO Secretary-General Jens Stoltenberg said on Thursday.
To prevent Moscow from succeeding, NATO and its member countries may have to continue to support Ukraine with arms and other assistance for a long time to come, he said.
"It's in our interest that this type of aggressive policy does not succeed," Stoltenberg said in a speech in his native Norway.
Describing what Moscow calls a "special military operation" as an attack on the current world order, Stoltenberg said the alliance had to prevent the war from spreading.
"This is the most dangerous situation in Europe since World War Two," he said.
"If President (Vladimir) Putin even thinks of doing something similar to a NATO country as he has done to Georgia, Moldova or Ukraine, then all of NATO will be involved immediately," Stoltenberg said. (Reporting by Jacob Gronholt-Pedersen and Nerijus Adomaitis; Writing by Terje Solsvik; Editing by Alison Williams and Tomasz Janowski)