Brussels/Moscow/Kyiv, 30 September 2022 (dpa/MIA) — NATO Secretary General Jens Stoltenberg condemned the Russian annexation of four Ukrainian provinces as "illegal and illegitimate." "This is the largest attempted annexation of European territory by force since World War II," Stoltenberg said in a press conference on Friday. "NATO Allies do not, and will not, recognize any of this territory as part of Russia," he said, calling on all states to reject the annexation. The top NATO official said the move "represents the most serious escalation since the start of the war" and pledged further support to Ukraine. Earlier on Friday, Russian President Vladimir Putin declared the four Ukrainian provinces of Luhansk, Donetsk, Zaporizhzhya and Kherson to be part of the Russian Federation as he signed a document to formally annex the regions occupied by Moscow's troops. The Russian president urged Kyiv to recognize the annexation of the regions, conducted after referendums a week ago that Moscow said showed an overwhelming majority in favor of leaving Ukraine and joining Russia. Kyiv and Western powers denounced the five-day vote, which ended on Tuesday, saying the results were a foregone conclusion that would never be recognized internationally. There were reports of residents being coerced into voting, sometimes at gunpoint. Putin also urged Ukraine to come to the negotiating table, in a bid to end the fighting that began when Russia invaded Ukraine in February. Ukrainian President Volodymyr Zelensky, however, ruled out negotiations with Putin. He said Ukraine is ready for dialogue with Russia, but only under a different Russian president. He also said his country is applying for an "accelerated" accession to NATO. "De facto, we have already started our path to NATO. Today, Ukraine is applying to make it de jure (legal)," Zelensky said in a video published on Telegram. NATO Secretary General Stoltenberg said a membership "remains open" to the country and that the alliance supports "Ukraine's rights to choose its own path to decide what kind of security arrangements it wants to be part of." However, he stressed the unanimity required among members for new applicants to join the alliance. As the terms of NATO's founding treaty considers an attack on one NATO ally an attack against all members – it is viewed as unlikely that the Western military alliance would allow a country at war like Ukraine to join the alliance. After Putin's speech, the European Union has vowed to never recognize the "illegal annexation" of the Ukrainian provinces. "Russia is putting global security at risk," read a joint statement from the 27 EU member states, calling on states and international organizations to reject the annexation. "These decisions are null and void and cannot produce any legal effect whatsoever. Crimea, Kherson, Zaporizhzhya, Donetsk and Luhansk are Ukraine," the statement read. Top representatives of the Organization for Security and Co-operation in Europe (OSCE) have condemned Moscow's moves to annex Ukrainian territories as "illegal" and "unacceptable." The organization, of which Russia is a member, once again called on Moscow "to withdraw all its forces from across Ukraine." The US announced it is imposing further sanctions on Russia, with measures targeting among others, further Russian government representatives, their family members and members of the military. "The United States condemns Russia’s fraudulent attempt today to annex sovereign Ukrainian territory," US President Joe Biden said on Friday. "The United States will always honor Ukraine’s internationally recognized borders." The areas annexed by Moscow have been occupied since soon after the start of Russian invasion. Putin said last week that Moscow would see Ukrainian attacks on the annexed regions as attacks on Russia itself and would use all means to defend them – a thinly veiled reference to nuclear weapons. Stoltenberg, meanwhile, said the military alliance will support Ukraine "to defend itself against Russia's aggression for as long as it takes." "Ukraine has, of course, the right to retake Ukrainian territory which is now occupied by Russian forces," Stoltenberg said speaking in Brussels. "If Russia stops fighting, there will be peace. If Ukraine stops fighting, it will cease to exist as an independent sovereign nation in Europe," Stoltenberg said. If NATO was to accept Russia's annexations and its "nuclear sable-rattling" and stopped supporting Ukraine, "then we would accept nuclear blackmailing," Stoltenberg said. "Russia must understand that a nuclear war can never be won and must never be fought." The use of nuclear weapons would have "severe consequences for Russia," he said. Together with Crimea, nearly 20% of Ukraine's territory is under Russian control, although Kyiv has reclaimed some of the occupied territory in recent weeks. But the Kremlin said on Friday that speculation it would resort to nuclear weapons are only designed to spread fear. "People who talk about nuclear escalation are acting very irresponsibly," said Kremlin spokesperson Dmitry Peskov.