Not true.
"Breeder" type reactors can be used to produce Plutonium-239 from Uranium-238. But that's a special kind of reactor, and in any case the P-239 which is produced is at low concentrations, spread throughout a larger mass of remaining U-238, and would be useless for making a weapon without a great deal of very high-tech extraction and purification (which itself would have to be done remotely, since the mass would be highly radioactive even from the beginning).
Non-breeder reactors, which are more common, do not produce more "fuel" than they start with, and therefore it is incorrect to say that "any" nuclear power plant makes U-235 or P-239 as a "natural byproduct".
There are of course less innocuous reactors... but that is NOT what I was talking about... and the states involved HAVE the type of reactors to make the raw materials.
Furthermore the high tech manufacturing equipment needed to build the one reactor can be EASILY retooled to make the other one, with little noticeable alteration.
Iran is purchasing a rocket protection system from China to protect their nuclear reactor plant... because it is JUST such a system.