Brussels, 15 March 2022 (dpa/MIA) — The NATO military alliance is to hold an extraordinary summit in Brussels on March 24 to coordinate its response to Russia's war in Ukraine, Secretary General Jens Stoltenberg said on Tuesday. "We will address #Russia’s invasion of #Ukraine, our strong support for Ukraine, and further strengthening NATO’s deterrence & defence. At this critical time, North America & Europe must continue to stand together," Stoltenberg wrote on Twitter. Almost simultaneously, an EU official confirmed that US President Joe Biden was to join an EU leaders' summit in Brussels next week to discuss their joint response to the war. Such a move is extremely rare for a US leader. The US president is to join leaders on the first day of the European Council summit on March 24. Further details were to be provided later in the day. The announcements came one day ahead of a special NATO meeting during which defense ministers are to consider the alliance's strategy to support members in Eastern Europe against the backdrop of the invasion. Speaking at a press conference earlier on Wednesday, Stoltenberg said further land, sea and air reinforcements to defend members on the eastern flank "for the longer term in all domains" were a possibility. Stoltenberg also outlined measures the alliance had taken since the start of the war. "There are now hundreds of thousands of forces on heightened alert across the alliance, 100,000 US troops in Europe and around 40,000 troops under direct NATO command, mostly in the eastern part of the alliance, backed by major air and naval power as well as air defenses," he said. With the risk of conflict spilling over into neighboring NATO members, the alliance chief said it was important to monitor borders closely and to stop incidents from escalating. A Russian missile attack on Sunday in a Ukrainian military training base near Poland's border killed 35 people and injured 134. In a separate incident, a Soviet-era drone crashed in Croatia after passing over the airspace of NATO members Romania and Hungary. Though NATO has not explicitly ruled out the prospect of membership for Ukraine — a key Russian demand — Ukrainian President Volodymyr Zelensky acknowledged on Tuesday that his country would not be joining the alliance. "For years we have heard about allegedly open doors, but we have also heard that we cannot enter there, this is true, we must admit this," Zelensky told the British-led Joint Expeditionary Force.