Produced by Japan's Toho (famously the studio of the Godzilla films), it's an end-of-the-world flick featuring a frankly astonishing international cast in what could be considered a "conference room drama" -- bottled-up high stakes human interaction in a true dystopic end to humanity. I can't figure how I never saw this back in the 80s; I only discovered it recently and I was blown away.
I'll second The Andromeda Strain, it's also a "conference room drama" and it really works. James Olson was a hugely underrated actor of the era.
Colossus: The Forbin Project, also wire-taut conference room drama with imminent destruction hanging on every decision.
And while we're at it, War Games, probably the best known of all these films, and maybe the only one that doesn't merit the categorization as a conference-room drama. But the stakes are the same.