Most nations probably want to avoid allowing that to come to pass - we're trying to stuff everything back into Pandora's Box that was let out after Trinity. I'd think of it more as one rival bringing a live grenade to a party to kill another, and everyone else brave enough to stick around trying to cool the tensions between the two.
Nukes are serious business. Truman would not allow MacArthur to dump nukes on NK when the war turned sour for the US, no matter how much he begged.
Edit: Things would have to get really, really ugly before nukes would be used. They're not cheap to produce, nor to maintain. And why waste a nuke on Cairo when you can keep it in reserve against Tehran?