Leaders of Europe’s most powerful political family want to make better use of the EU’s mutual defense clause amid growing concerns about Donald Trump’s commitment to NATO.

The push came during a weekend dinner at a European People’s Party leaders’ retreat in Zagreb, Croatia featuring the likes of German Chancellor Friedrich Merz and European Commission President Ursula von der Leyen, as reported in Brussels Playbook.

The EPP will task two as-yet-unnamed heads of state or government with looking at how to implement the EU Treaty’s Article 42.7 (which obliges countries to provide “aid and assistance by all the means in their power” if an EU country is attacked).

The EPP top brass did not make clear by when the leaders will have to deliver this plan or what exactly it will address. However, a policy paper published by the EPP on Sunday pointed to nine areas where the EU needs to develop military capacity if it’s to become independent of the U.S., including drones, space and missile defense. The EPP’s policy paper still makes mention of NATO as the cornerstone of European defense.

The push to use the EU’s mutual defense clause comes amid the worst transatlantic crisis in decades, with Trump’s claim to Greenland shaking belief in the U.S. commitment to NATO.

During a press conference in Zagreb, EPP President Manfred Weber praised French President Macron for his offer to extend France’s nuclear umbrella to other EU states. “Having the new U.S. developments in mind,” said Weber, “I am totally in favor that the leaders are … considering how this option of a French nuclear weapon can be used for European security.”