This is possible, or it might just be Trump copying Carney. i.e. Carney is the self-made economic guru that Trump has tried to portray himself as. Carney is the one making big waves by diversifying Canada's markets in response to Trump's grab for power over Canada. Potash is one of the things people immediately point to whenever Trump says the U.S. doesn't need anything Canada has. So, now he's going to find a new supplier in order for the U.S. to be less reliant on Canada. Belarus is never going to be able to produce more than a tiny fraction of what the U.S. needs, plus there's the transport issue. Maybe some kick-backs made it worth doing anyways. Who knows?
At the same time, Trump is making a big show of passing (or just threatening) new sanctions on Russia and anyone who trades with them (because midterms). Given that a lot of this Belarusian potash is likely to travel through Russia (if it doesn't actually come from Russia), and Belarus is basically just an extension of Russia now anyways, wouldn't this mean Trump should threaten the U.S. with his new sanctions?
Trump missed his true calling. He should have done comedy.