BERLIN, Germany -- The war in Ukraine could last "for years", NATO chief Jens Stoltenberg warned in an interview published Sunday by German daily newspaper Bild, while reiterating calls for Western countries to provide long-term support to Kyiv.

"We must be prepared for this to last for years," the secretary general of the North Atlantic Treaty Organization said.

"We must not weaken in our support of Ukraine, even if the costs are high -- not only in terms of military support but also because of rising energy and food prices."

He told Bild that the food and fuel costs are nothing compared to the one paid daily by Ukrainians on the frontline, warning "we would have to pay an even greater price" if Russian President Vladimir Putin were to achieve Moscow's goals in Ukraine.

The NATO chief has in the past week ramped up calls for alliance members to back Ukraine in its fight against Russia's invasion.

Repeating his calls for NATO member nations to continue delivering weapons to Kyiv, Stoltenberg said the hardware support could increase "the likelihood of Ukraine being able to push Putin's troops out of the Donbas region".

The easternmost Donbas region of Ukraine is currently partly under the control of Russian forces.

Ukrainian defence minister Oleksiy Reznikov and other officials this week met with around 50 countries of the Ukraine Defence Contact Group at NATO headquarters to ask for a surge in weapons and ammunition.