NATO has declared Russia the "most significant and direct threat” to its members’ peace and security amid Moscow's unprovoked invasion of Ukraine.
The Western military alliance made the declaration in a statement as its leaders met in Madrid on June 29 to confront what NATO chief Jens Stoltenberg called the biggest security crisis since World War II.
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NATO's declaration underscores how dramatically Russia’s invasion of Ukraine has unsettled Europe’s post-Cold War security order.
The alliance also promised to “step up political and practical support” to Ukraine in the face of Russia’s invasion.
Stoltenberg said Ukraine is fighting for its independence but also for Western values and security.
But Ukrainian President Volodymyr Zelenskiy, in a video address to the summit, chided NATO for not embracing his embattled country more fully and asked for more weapons to defeat Moscow's forces.
Zelenskiy told NATO leaders that Ukraine needs more advanced heavy weapons and additional financial support to stave off Russia's invasion, warning that Moscow's ambitions won't stop with his country.
"We need to break the Russian artillery advantage.... We need much more modern systems, modern artillery," Zelensky told a NATO summit in Madrid via video link on June 29, adding that financial support was "no less important than aid with weapons."
"This is not a war being waged by Russia against only Ukraine. This is a war for the right to dictate conditions in Europe -- for what the future world order will be like," Zelenskiy said.
The statement also said that NATO leaders agreed on June 29 to formally invite Finland and Sweden to join the alliance after Turkey struck a deal with the Nordic duo to drop its objections.
SEE ALSO: Zelenskiy Asks NATO Allies For Modern Heavy Weapons, More Financial Support"Today, we have decided to invite Finland and Sweden to become members of NATO and agreed to sign the Accession Protocols," a declaration from a summit in Madrid said.
Russia's war on Ukraine raised fears in Finland and Sweden, prompting them to seek to join the 30-member alliance. Finland's long border with Russia means the Russian-NATO border will expand dramatically.
Finland and Sweden applied to join the military alliance last month, but their bids were held back by Turkey, which has accused both nations, particularly Sweden, of offering a safe haven to Kurdish militants who have been waging an insurgency against the Turkish state.
Stoltenberg also said he expected a swift ratification of Sweden and Finland joining the military alliance. Unanimous consent is required for NATO enlargement.
Russian President Vladimir Putin said Russia would respond in kind if NATO set up infrastructure in Finland and Sweden after they join the alliance. According to Russian news agencies, he also said he could not rule out that tensions would emerge in relations with Helsinki and Stockholm over their membership in NATO.
U.S. President Joe Biden thanked Turkish President Recep Tayyip Erdogan for dropping his opposition to Sweden and Finland’s membership bids. At the same time, a Pentagon official signaled support for Turkey's plan to purchase additional F-16 warplanes.
Celeste Wallander, assistant secretary of defense for international security affairs, told reporters on a conference call that the U.S. Defense Department “fully supports Turkey's modernization plans."
"Turkey is a highly capable, highly valued, strategic NATO ally, and Turkish defense capabilities -- strong Turkish defense capabilities -- contribute to strong NATO defense capabilities," she said.
A plan to equip Turkey with F-35 stealth fighters fell through after Turkey bought S-400 anti-aircraft missile systems from Russia, which the United States considered threatening to the security of the F-35 program.
Turkey then set out to buy new F-16 fighter jets, as well as upgrades for its existing fleet of the same planes, but that purchase was put on hold.
WATCH: Polish and Lithuanian leaders have expressed support for Ukraine and stressed the need for additional military assistance to Kyiv in the face of the ongoing Russian invasion. Polish President Andrzej Duda and Lithuanian President Gitanas Nauseda talked to RFE/RL on the sidelines of the NATO summit in Madrid on June 29.
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Polish, Lithuanian Leaders Call For More Military Help For Ukraine At NATO Summit
Biden said earlier that the United States is strengthening its military presence in Europe in the face of new threats posed by Russia's invasion of Ukraine.
Biden said the alliance will be "strengthened in all directions across every domain -- land, air, and sea."
Biden said at a meeting with Stoltenberg that Washington was boosting the fleet of U.S. naval destroyers from four to six in Rota, Spain, and would establish a permanent headquarters in Poland of the 5th Army Corps.
It will also send an "additional rotational brigade" to Romania, consisting of "3,000 fighters and another 2,000 personnel combat team" and will enhance rotational deployments in the Baltic countries, Biden said.
Two additional squadrons of the F-35 stealth plane will be sent to Britain and more air defense and other capabilities will be placed in Germany and in Italy.
"We're sending an unmistakable message...that NATO is strong, united, and the steps we're taking during this summit are going to further augment our collective strength," Biden said.
"We mean it when we say an attack against one is an attack against all," he told reporters at the start of a working session of NATO leaders.