We would likely deal with it the same way we did with nuclear proliferation.

For countries that don't have nukes and try to get them, we use economic pressure, then sabotage (Stuxnet), then assassinations, then actual bombs. And we have done all of those steps several times.

We almost bombed China to stop them from getting nukes, and arguably the only reason they have nukes today is because they had Jewish support and espionage feeding them support while stopping our response.