U.S. negotiators asked whether Ukraine would withdraw its troops from the remaining Ukrainian-controlled parts of Donbas in exchange for NATO membership, President Volodymyr Zelensky said, according to Reuters.

Such a withdrawal would mean Ukraine giving up positions it still holds in the region. Zelensky said Ukraine would not recognize occupied territory as legally Russian.

Speaking to journalists Friday, Zelensky said it was the first time American negotiators had raised that possibility. The discussion has not produced a concrete proposal, Interfax-Ukraine reported. No agreement or NATO invitation has been announced.

Zelensky said a comprehensive package involving security guarantees, military support and reconstruction funding would need to be put before the Ukrainian public.

Separately, Zelensky warned that discussions about a broader European security framework before the war ends could benefit Russian President Vladimir Putin by weakening NATO and allowing Moscow to pursue changes to Europe’s borders, The Associated Press reported.