He was speaking after NATO Secretary-General Mark Rutte announced that NATO would launch a new mission called "Baltic Sentry" to strengthen the protection of critical undersea infrastructure.
The gathering in the Finnish capital marked the launch of the new initiative for joint monitoring and exercises in the Baltic Sea region.
Tusk told reporters that an increasingly aggressive Russian posture in the Baltic had prompted "unprecedented" decisions.
"In this case, it means a radical strengthening of NATO’s presence in the Baltic Sea," he said at a press conference.
While acts of sabotage have directly affected Sweden, Finland and Estonia, "all countries obviously feel threatened," Tusk said.
During the meeting, Rutte outlined the objectives of Baltic Sentry, which include regular patrols, joint exercises, and enhanced surveillance of key installations.
The initiative will involve allied naval and submarine forces, reconnaissance aircraft, and advanced technologies such as a fleet of maritime drones.
The leaders did not specify how individual countries would contribute to the initiative, Polish state news agency PAP reported.
'Greenland remains part of Denmark'
The Helsinki talks also touched on global security, including recent statements by US President-elect Donald Trump about Greenland.
Last week, Trump claimed the United States needed the world's largest island for national security reasons and questioned whether Denmark had legitimate sovereignty over it.
Tusk stated that "Greenland remains part of Denmark" and noted that some remarks and proposals from the incoming US administration—such as annexing Canada, purchasing Greenland, and reclaiming the Panama Canal—had sparked international concerns.
However, he stressed that all leaders at the Helsinki meeting agreed on the fundamental importance of transatlantic cooperation.
"Regardless of how challenging this may be today, European-American relations are invaluable," Tusk said. "Neither Ukraine nor Europe, nor the United States will be able to defend this part of civilisation from aggressive global powers if we are divided and in conflict."
The Helsinki meeting was attended by leaders including German Chancellor Olaf Scholz, Danish Prime Minister Mette Frederiksen, Latvian President Edgars Rinkēvičs, Lithuanian President Gitanas Nausėda, Swedish Prime Minister Ulf Kristersson, and European Commission Vice President Henna Virkkunen.
(rt/gs)
Source: IAR, PAP