In front of an audience of thousands in Lithuania’s capital on Wednesday, President Joe Biden had a message for the United States’ North Atlantic Treaty Organization allies and the Ukrainian fighters working to repel a Russian invasion: “our unity will not falter, I promise you.”

Bookending his speech in Vilnius, Lithuania with remarks on the country's liberation from the Soviet Union in the early 1990s, Biden made the case for the U.S.-led international order within and beyond Europe that he has prioritized rebuilding and strengthening during his first term, while laying out his optimistic vision for a world united against “other would-be aggressors” and the climate crisis.

“As I look around the world today, at the moment of war and peril, a moment of competition and uncertainty. I also see a moment of unprecedented opportunity,” Biden said, speaking in a courtyard at Vilnius University to a crowd the White House said included almost 10,000 people. “We need to take the same spirit of unity, common purpose, determination that we've demonstrated in our response to Russian aggression in Ukraine and bring more partners along as we continue working to build a world we want to live in. And a world we want for our children.”

Biden said the United States “will not waver” in its support for Ukraine after the conclusion of a NATO summit in Vilnius that progressed Sweden’s ascension to the alliance and strengthened ties with Ukraine even as a pathway to the latter nation’s NATO membership remained far off.

“When Putin and his craven lust for land and power unleashed his brutal war on Ukraine. He was betting NATO would break apart,” Biden said. “The United States stepped up, NATO stepped up, our partners in Europe and then the Indo Pacific stepped up. All across the world. they stepped up.”

Earlier on Wednesday, Biden stood alongside NATO leaders and Ukrainian President Volodymyr Zelenskyy as they announced the formation of a NATO-Ukraine Council, which would increase cooperation and communication between the alliance and the war torn nation. Biden and NATO pledged to help build up Ukraine’s military for the duration of the war and beyond.

“Ukraine’s future lies with NATO,” Biden said at the announcement, later joking he would like to see Ukraine join NATO “an hour and 20 minutes” after the war’s end.

Any path to membership is unlikely to begin until after the war. An attack on any NATO nation is considered to be an attack on all and members would be required to leap to their besieged ally’s defense. While eager to help fund and supply Ukraine’s war effort, the United States and its European allies are not willing to engage in direct conflict with Russia and risk a showdown between nuclear powers.

"The results of the summit are good, but if there were an invitation, that would be ideal," Zelenskyy said earlier on Wednesday, through a translator, after previously calling the absence of a solid commitment ”unprecedented and absurd.”

After the speech, on the tarmac at a Vilnius airport, Biden said the Ukrainian leader “understands whether or not he is in NATO now is not relevant” because of NATO’s commitment to continue their material support to Ukraine’s defense, according to a pool report.

Biden landed in Helsinki, Finland on Wednesday night ahead of meetings with the leaders of Nordic countries on Thursday.

During the speech, Biden had high praise for the Ukrainian people and soldiers currently fighting a counteroffensive to retake captured territory from Russia. 

“We rallied the world to support the brave people in Ukraine as they defend their liberty and their sovereignty with incredible dignity,” he said. “After nearly a year and a half of Russia’s forces committing terrible atrocities, including crimes against humanity, the people of Ukraine remain unbroken. Ukraine remains independent, remains free.”

At the airport, Biden said he had been briefed on the counteroffensive but couldn’t disclose details publicly. He also said sending missiles with longer ranges than the weapons Ukraine currently has was on the table, according to a pool report.

“Our commitment to Ukraine will not weaken. We will stand for liberty and freedom today, tomorrow and for as long as it takes,” Biden added, echoing the sentiment NATO leaders expressed at the summit.

Lithuanian President Gitanas Nausėda heralded Biden’s presence in his country in brief remarks before the U.S. president spoke, calling him “a close friend and ally” and noted “America’s presence in Lithuania strengthens our security. America’s assistance to Ukraine strengthens its ability to resist the occupier,” according to a translation published by Nausėda’s office.

“We are primarily responsible for our defense ourselves. However, the active engagement of the United States allows us to mitigate long-term threats we know all too well from history,” Nausėda said of his country which shares borders with Russia-aligned Belarus and a non-contiguous Russian territory, the Kaliningrad Oblast on the Baltic Sea.

Onlookers waved Ukrainian flags and chanted “glory to the heroes” in support of the Ukrainian soldiers as Nausėda spoke, a Polish journalist noted.

Beyond Ukraine, Biden emphasized the unity NATO and Europe displayed after the Russian invasion should be capitalized on in concert with allies in Asia and the Pacific to take on global challenges like “the existential threat of accelerating climate change,” the next pandemic, the rapid growth of artificial intelligence, and the development of poorer nations.

“The world has shrunk,” Biden said. “We have to step up together, building the broadest and deepest coalition to strengthen and defend the basic rules of the road, to preserve all the extraordinary benefits that stem from the international system grounded in the rule of law.”

Even as the bodies continue to pile up in Ukraine and the planet saw its hottest days in recorded history just this past week, Biden assured his audience in Lithuania and around the world that he was confident better days are ahead. 

“Folks, the road that lies before us is hard, will challenge us — some of the best of ourselves — to hold faith in one another and never give up. Never lose hope never,” Biden said near the end of his remarks. “Some have heard me say to my country many times: never ever in my entire career have I been more optimistic about the prospects of the future.”