With the heads of NATO countries descending on Vilnius today for two days of talks, Russia's war in Ukraine - and the prospect of the war-torn nation joining the security alliance - is at the top of the agenda.
Kyiv sees membership as the ultimate deterrent against Russia attacking Ukraine again, after it illegally annexed Crimea in 2014 and launched a full-scale invasion in February last year.
But Putin and the Kremlin have long pointed to NATO's expansion eastwards as one of the factors that triggered their decision to invade in the first place.
US President Joe Biden this weekend declared Ukraine is not yet ready for NATO membership, arguing that the war with Russia needs to be concluded before the security alliance can extend an invitation to Kyiv.