The top US diplomat reiterated the "rock solid" determination of his country and other members to eventually include Ukraine in the military bloc at a NATO summit in Brussels this week. Speaking alongside Ukrainian Foreign Minister Dmitry Kuleba, he said the purpose of the event was to "help build a bridge to membership."

"This is literally how the nuclear apocalypse movie starts," Musk responded on X (formerly Twitter).

He shared a video from the 1983 American television film 'The Day After', which depicts a fictional nuclear war between the US and the USSR. The movie was shown to Soviet audiences in 1987, when the two superpowers were negotiating a key nuclear arms control treaty.

Moscow has cited NATO expansion in Europe against Russian objections and an intention to include Ukraine in the organization as one of the key causes of ongoing hostilities. The US and its allies have claimed that all nations have a right to seek accession regardless of whatever concerns Russia may have.

Musk has previously spoken out about the risks to Ukraine and the world of further escalation. Continued hostilities could result in Kiev losing access to the Black Sea, he said last week.

The billionaire has urged Kiev to offer concessions to Moscow in exchange for a peace treaty. He has also backed the argument that US attempts to weaken Russia by arming and funding Ukraine have backfired.