U.S. President Joe Biden and world leaders opened a trio of emergency summits on Thursday with a sober warning from NATO Secretary-General Jens Stoltenberg that the alliance must boost its defenses to counter Russia’s invasion of Ukraine and “respond to a new security reality in Europe.” Stoltenberg commented as he called to order a NATO summit focused on increasing pressure on Russian President Vladimir Putin over the assault on Ukraine while tending to the economic and security fallout spreading across Europe and the world. “We gather at a critical time for our security,” Stoltenberg said, addressing the leaders seated at a large round table. “We are united in condemning the Kremlin’s unprovoked aggression and in our support for Ukraine’s sovereignty and territorial integrity.” He said the alliance is “determined to continue to impose costs on Russia to bring about the end of this brutal war.” Over the course of Thursday, the European diplomatic capital is hosting the emergency NATO summit, a gathering of the Group of Seven industrialized nations and a summit of the European Union. Biden will attend all three meetings and hold a news conference afterward. The schedule left Brussels interlaced with multiple police checkpoints and road closures to help motorcades crisscross the city as the leaders go from one meeting to the next. Biden arrived late Wednesday with the hopes of nudging allies to enact new sanctions on Russia, which has seen its economy crippled by several weeks of bans, boycotts and penalties. While the West has been largely unified in confronting Russia after it invaded Ukraine, there’s wide acknowledgement that unity will be tested as the costs of war chip at the global economy. The bolstering of forces along NATO’s eastern flank, almost certainly for at least the next five to 10 years if Russia is to be effectively dissuaded, will also put pressure on national budgets. “We need to do more, and therefore we need to invest more. There is a new sense of urgency and I expect that the leaders will agree to accelerate the investments in defense,” Stoltenberg said before the summit. Biden’s national security adviser, Jake Sullivan, said the U.S. wants to hear “that the resolve and unity that we’ve seen for the past month will endure for as long as it takes.” The energy crisis exacerbated by the war will be a particularly hot topic at the European Council summit, where leaders from Spain, Portugal, Italy and Greece are hoping for an urgent, coordinated bloc-wide response. EU officials have said they will seek U.S. help on a plan to top up natural gas storage facilities for next winter, and they also want the bloc to jointly purchase gas. German Chancellor Olaf Scholz has dismissed calls to boycott Russian energy supplies, saying it would cause significant damage to his country’s economy. Scholz is facing pressure from environmental activists to quickly wean Germany off Russian energy, but he said the process will have to be gradual.