NATO chief Jens Stoltenberg has pledged the alliance’s support for Ukraine “for as long as it takes” and has reiterated that the door to membership in the world’s largest security organization remains open to all, including Kyiv, writes rferl.com.

Speaking in Bucharest on November 29 as U.S. Secretary of State Antony Blinken and the other NATO foreign ministers gathered in Romania, Stoltenberg called on partners to step up aid for Ukraine, whose energy infrastructure has been devastated by a barrage of Russian attacks at the onset of the winter season.

“Our message from Bucharest is that NATO will continue to stand with Ukraine for as long as it takes. We will not back down,” Stoltenberg told a conference in the Romanian capital ahead of the ministerial meeting.

He added that the only way to get the right terms for negotiations with Moscow to begin would be for Ukraine to advance on the battlefield.

“To create the conditions for a lasting peace, which ensures that Ukraine prevails as an independent sovereign state, we must continue to provide military support to Ukraine,” he said.

Stoltenberg separately told journalists that NATO allies will ramp up aid for Ukraine as Russian President Vladimir Putin uses “winter as a weapon of war” because his forces are failing on the battlefield.

“We have delivered generators and spare parts, and the allies are helping to rebuild destroyed infrastructure,” he said, adding that the Bucharest gathering would serve as a platform to drum up Western aid to rebuild Ukraine’s energy infrastructure.

Stoltenberg reaffirmed the military alliance’s commitment to admitting new members, including Ukraine, without offering a precise date.

“NATO’s door is open,” Stoltenberg said.

“Russia does not have a veto” on countries joining, he said, adding that Putin “will get Finland and Sweden as NATO members” soon. The Nordic neighbors applied for membership in April, concerned that Russia might target them next.

“We stand by that, too, on membership for Ukraine,” Stoltenberg said. “At the same time, the main focus now is on supporting Ukraine, ensuring that President Putin doesn’t win, but that Ukraine prevails as a sovereign nation in Europe.”

He also warned that Europe should brace for the arrival of more Ukrainians fleeing worsening conditions at home.

“We have to be prepared for more refugees crossing into the rest of Europe,” as a result of Russia’s “deliberate attack on critical services, heating, light, water, gas” in Ukraine, Stoltenberg said.