NATO doubled down Tuesday on its commitment to one day include Ukraine, a pledge that some officials and analysts believe helped prompt Russia’s invasion this year. The world’s largest security alliance also pledged to send more aid to Ukrainian forces locked in battle with Russian troops.

U.S. Secretary of State Antony Blinken met with NATO foreign ministers in Romania to drum up support for Ukraine as Russia bombards energy infrastructure ahead to the frigid winter. Russia cannot stop the alliance’s expansion, NATO leaders said.

“NATO’s door is open,” NATO Secretary-General Jens Stoltenberg said before chairing the meeting in the capital, Bucharest.

He praised North Macedonia and Montenegro recently joining NATO, and said that Russian President Vladimir 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.

“Russia does not have a veto” on countries joining, Stoltenberg said. “We stand by that, too, on membership for Ukraine.”

When they met in Bucharest in 2008, NATO leaders said that Ukraine and Georgia would join the alliance one day.

Some officials and analysts believe that move — pressed on the NATO allies by former U.S. President George W. Bush — was partly responsible for the war that Russia launched on Ukraine in February. Stoltenberg said NATO expansion would not be hindered.

“President Putin cannot deny sovereign nations to make their own sovereign decisions that are not a threat to Russia,” the former Norwegian prime minister said. “I think what he’s afraid of is democracy and freedom, and that’s the main challenge for him.”

Even so, Ukraine will not join NATO anytime soon. With the Crimean Peninsula annexed, and Russian troops and pro-Moscow separatists holding parts of the south and east, it’s not clear what Ukraine’s borders would even look like.

Many of NATO’s 30 allies believe the focus now must solely be on defeating Russia, and Stoltenberg stressed that any attempt to move ahead on membership could divide them.

“We are in the midst of a war and therefore we should do nothing that can undermine the unity of allies to provide military, humanitarian, financial support to Ukraine, because we must prevent President Putin from winning,” he said.

Beyond Ukraine’s immediate needs, NATO wants to see how it can help the country longer-term, by upgrading its Soviet-era equipment to the alliance’s modern standards and providing more military training.

Slovak Foreign Minister Rastislav Kacer said the allies must help Ukraine so that “the transition to full membership will be very smooth and easy” once both NATO and Kyiv are ready for accession talks.

In a statement, the ministers vowed to help Ukraine rebuild once the war is over, saying: “we will continue to strengthen our partnership with Ukraine as it advances its Euro-Atlantic aspirations.”

Ukraine, for its part, called for more supplies of weapons to defend itself with, and quickly.

“Faster, faster and faster,” Foreign Minister Dmytro Kuleba said. “We appreciate what has been done but the war goes on.”

“In a nutshell,” he said, “Patriots (missiles) and transformers is what Ukraine needs the most.”

Some ministers made pledges of military support for Ukraine, others for financial and nonlethal aid.

Slovakia said that it was providing 30 armored personnel carriers and more artillery.

During the two-day meeting, Blinken will announce substantial U.S. aid for Ukraine’s energy grid, U.S. officials said. Ukraine’s network has been battered countrywide since early October by targeted Russian strikes, in what U.S. officials call a Russian campaign to weaponize the coming winter cold.

Estonia’s foreign minister, Urmas Reinsalu, went a step further than most, calling on his NATO partners to pledge 1% of their GDP to Ukraine in military support, saying it would make “a strategic difference.”

Most NATO allies, however, are struggling to spend 2% of GDP on their own defense budgets.

The foreign ministers of NATO candidates Finland and Sweden are joining the talks. NATO is eager to add the two Nordic nations to the defensive forces lined up against Russia. Turkey and Hungary are the holdouts on ratifying their applications. The 28 other member nations have already done so.