"We should also be prepared for bad news," he said, when asked if he feared that the situation in Ukraine would worsen in the future.
"Wars develop in phases. But we have to support Ukraine in both good and bad times," he said, TASS reported.
It is crucial to boost ammunition production, Stoltenberg said, conceding that NATO countries were unable to meet the increased demand for them. He said Ukraine is now in a "critical situation," but declined to recommend what Kiev should do.
"I will leave it to the Ukrainians and military commanders to make these difficult operational decisions," Stoltenberg said.
He also commented on challenges faced by the European defense industry.
"One of the issues we should address is the fragmentation of the European defense industry," he said.
The NATO chief said it’s in the interest of Europe and is good for jobs in the industry. He said it is important not to allow ammunition prices to rise now that demand has climbed.
Stoltenberg said there had been no significant developments on the battlefield over the past few months. He declined to share an outlook for what could happen next.
"Wars are inherently unpredictable," the official said. "But we know that the more we support Ukraine, the faster the war will end.".