He said this in an interview with the BBC, Ukrinform reports.
According to the media outlet, Stoltenberg has been trying to persuade other countries to commit more money to the war effort in Ukraine in recent days in the hope of a five-year, EUR 100 billion fund.
"He [Stoltenberg] said he was confident he would get an agreement by July, despite some countries expressing hesitation this week," the news story reads.
Read also: NATO not going to send troops to Ukraine - StoltenbergLong-term support was vital now, and to rebuild the country after the conflict, he said.
"Even if we believe and hope that the war will end in the near future, we need to support Ukraine for many years, to build their defenses to deter future aggression," he said.
Stoltenberg said that military support was vital to repel Russian forces from Ukraine and force Putin to give up his goals of occupation. He also suggested that Ukraine might ultimately have to make concessions too.
"At the end of the day, it has to be Ukraine that decides what kind of compromises they're willing to do, we need to enable them to be in a position where they actually achieve an acceptable result around the negotiating table," he said.
Stoltenberg earlier proposed creating a fund of allies' contributions worth $100 billion over five years for Ukraine as part of the package that NATO leaders are to sign in Washington in July.
Photo: Europa Press