The former Yugoslav republics of Macedonia and Montenegro should be invited to join NATO when it holds its next summit in Warsaw in 2016, Polish Defense Minister Tomasz Siemoniak said on Friday.
Such a move could further fan tensions between the western alliance and Russia, already running high over the crisis in Ukraine.
"It would be excellent news if the invitations could be sent from (the NATO summit in) Warsaw to Macedonia and Montenegro," Siemoniak told a conference in the Polish city of Wroclaw.
"It seems that the NATO summit in Warsaw, if deprived of this element, will not bring full satisfaction to many nations, including Poland."
Macedonia and Montenegro want to follow in the footsteps of Albania and ex-Yugoslav Croatia, which joined NATO in 2009.
But Russia has opposed any NATO expansion to former communist nations of eastern and southeast Europe, part of a competition for geostrategic influence since the end of the Cold War that lies at the heart of the current conflict in the former Soviet Ukraine.
Russian Foreign Minister Sergei Lavrov said last year that NATO expansion to the former Yugoslav republics of Bosnia, Macedonia and Montenegro could be seen as a provocation.
At its last summit in 2014 in Wales, the alliance approved wide-ranging plans to boost its defenses in eastern Europe, aiming to reassure allies nervous about Russia's intervention in Ukraine that NATO would shield them from any attack.
The Warsaw summit will take place on July 8-9, 2016.