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.
Most dangerous
"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.
"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."
NATO Secretary-General Jens Stoltenberg