European Union leaders on Thursday committed to a massive step in defense cooperation following decades of hesitation, spurred by U.S. President Donald Trump ’s repeated warnings that he would cut them adrift to face the threat of Russia without America's overwhelming military might.

EU leaders and Ukrainian President Volodymyr Zelenskyy were to meet to discuss boosting European countries' defense spending. Meanwhile, France's Emmanuel Macron showed openness to sharing Paris' nuclear deterrent.

European Union leaders are holding emergency talks on ways to quickly increase their military budgets after the Trump administration signaled that Europe must take care of its own security and also suspended assistance to Ukraine.