The U.S. has proposed security guarantees for Ukraine similar to — but separate from — the collective defense agreement between NATO member countries, Italy’s premier and a diplomatic source said on Saturday.

The suggestion was raised during a call U.S. President Donald Trump held with Ukrainian President Volodymyr Zelensky and European leaders on Saturday, the day after Trump’s summit with Russia’s Vladimir Putin.

“As one of the security guarantees for Ukraine, the American side proposed a non-NATO Article 5 type guarantee, supposedly agreed with Putin,” the diplomatic source told AFP on condition they not be identified in any way.

NATO’s collective security is based on its Article 5 principle: if one member is attacked, the entire alliance comes to its defense.

Italian Prime Minister Giorgia Meloni, who was on the call with Trump, confirmed the U.S. president had raised the idea of security guarantee “inspired” by Article 5, which she has been pushing for several months.

The starting point for the proposal was defining a collective security clause “that would allow Ukraine to benefit from the support of all its partners, including the U.S., [which would be] ready to act in case it is attacked again,” Meloni said in a statement.