On the other hand, if Russian President Vladimir Putin lays down arms, peace will ensue.

Stoltenberg emphasized that most wars last longer than initially expected. He pointed out that the cessation of hostilities from either side would have significant consequences.

If Ukraine stops fighting, it risks losing its sovereignty, while if Russia stops, peace could be achieved.

The NATO chief also highlighted the need for security guarantees for Ukraine in the post-conflict period to prevent history from repeating itself.

He expressed no doubt that Ukraine would eventually become a NATO member, reiterating his support for Ukraine's long-term accession to the alliance.

Related video: Ukraine invites arms manufacturers to Kyiv as NATO leaders demand greater urgency in production (Dailymotion)

Stoltenberg also called on Germany to significantly increase its defense spending.

He reminded that during the Cold War era, defense expenditures were between three to four percent of the GDP. He expects many allies to exceed the current minimum target of two percent of GDP set at the NATO summit in Vilnius.

(With inputs from agencies)