The leaders of five European Union countries urged their neighbors and allies Wednesday to ramp up military support for Ukraine, while the bloc’s defense ministers debated ways to help meet the war-ravaged country’s ammunition shortfall.

In their appeal, the leaders of the Czech Republic, Denmark, Estonia, Germany and the Netherlands warned that Europe’s security is tied to the fighting that started almost two years ago with Russia‘s invasion of its neighbor.

“Our ability to continue to support and sustain Ukraine’s defense, both during the winter and in the longer term, is decisive,” they wrote in the Financial Times newspaper. “In fact, it is a matter of our common European security.”