Tusk, whose country is a staunch supporter of Kyiv, spoke in Warsaw alongside European Council head Charles Michel, who urged member countries to invest more in defence.

"From the first days of the war, Poland has given Ukraine everything possible and even more. Today, Poland... has to also build its own security," Tusk told reporters.

"We have to as a whole -- not Poland alone -- help Ukraine as much as possible, but all of Europe must also slowly think more actively on how to help countries like Poland and Estonia, countries on the frontline," he said.

"If we are one Europe, then that means the war is at our doorstep. And that's why we will look for all possible ways to support Ukraine and to support the countries that are the most vulnerable to this war's consequences."

Tusk, whose country already spends around four percent of gross domestic product on defence, spoke ahead of a working dinner in Warsaw with Michel and several European heads of government.

"Today we face extraordinarily difficult geopolitical challenges," Michel told reporters.

"We have to support Ukraine as much as we can. We have to develop our defence capabilities, to develop our defence readiness, to invest more in defence," he said.

Tusk last month warned of the "real" threat of conflict in Europe, saying that for the first time since the end of World War II, the continent has entered a "pre-war era".