"For the safety of Europe, it is better to have Ukraine in NATO, where it cannot make national decisions on territorial claims," Kissinger told The Economist.
Putin has said that one of his objectives for starting the war in Ukraine was preventing the expansion of NATO on Russia's borders. That goal backfired when Finland and Sweden were motivated by the invasion of Ukraine to apply to join the military bloc.
Putin also said during a press conference shortly before the war began that Ukraine joining NATO might increase the chances of a Russia-NATO conflict that could turn nuclear.