The meeting, held on the sidelines of the Ukraine Recovery Conference in the northern Polish city of Gdańsk, brought together leaders from Poland, Lithuania, Latvia, Estonia, Finland, Sweden and Romania, along with representatives of the European Commission.
Polish Prime Minister Donald Tusk said the countries had demonstrated "complete unity and complete solidarity" in the face of growing security risks.
"Let this be a warning sign to anyone planning anything harmful against any of us or our countries," Tusk told reporters after the meeting.
He said participants agreed that strong transatlantic ties and close defence cooperation with the United States remained essential to European security.
"No one here has any doubts that the American presence and cooperation with the United States serve the security of Europe and our countries well," Tusk said.
He added that leaders also shared the view that the security situation remained highly unstable and that further escalation could be expected in the coming weeks and months.
"As countries directly exposed to this risk because we border Russia, Belarus and Ukraine, we will work very closely together to prepare coordinated responses should anything happen," he said.
Tusk noted that eastern flank countries were among NATO's biggest defence spenders, with Poland expected to allocate nearly 7 percent of its gross domestic product to defence this year.
Lithuanian President Gitanas Nausėda said the meeting was an opportunity to coordinate positions ahead of the NATO summit, stressing the importance of collective defence under Article 5 of the alliance's founding treaty, continued support for Ukraine and recognition of Russia as a long-term threat.
"We must do everything possible to convince Washington that a strong US presence on NATO's eastern flank strengthens the alliance," Nausėda said. "A strong eastern flank means a stronger Europe."
Romanian President Nicușor Dan called for NATO unity "from north to south and from east to west," citing repeated incidents involving Russian drones violating the airspace of eastern flank countries.
He also said the European Union and NATO should play complementary roles in strengthening Europe's defence while allies continue increasing military spending.
Finnish Prime Minister Petteri Orpo highlighted progress in regional defence cooperation, pointing to the Eastern Sentry initiative, a multinational effort to improve air defence and counter hostile drones along NATO's eastern border.
The initiative was launched after Russian drones briefly entered Polish airspace in September last yeaa, prompting several NATO members to deploy additional military assets to the alliance's eastern flank.
Estonian Prime Minister Kristen Michal said Europe's defence now begins on the European Union's eastern border and called for faster military mobility and greater support for Ukraine.
"The recent drone incidents have shown that Europe must act faster, support Ukraine more and increase pressure on Russia," he said.
Latvian Prime Minister Andris Kulbergs said European countries might compete economically in peacetime but had become "more united than ever" in supporting Ukraine and strengthening regional security.
European Defence Commissioner Andrius Kubilius said countries on NATO's eastern flank were carrying much of the burden of Europe's increased defence spending.
He described the Eastern Sentry initiative as one of the European Commission's flagship defence projects and said eastern flank countries would receive EUR 76 billion under the EU's SAFE rearmament programme.
"That is European solidarity in action," Kubilius said.
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Source: IAR, PAP