Billionaire businessman Donald Trump had some harsh words for President Obama this week, calling the White House leader’s remarks about a nuclear disaster in downtown New York City one of the dumbest ever.

Mr. Obama told reporters this week in Belgium that Russia’s aggression into Ukraine and annexation of Crimea didn’t worry him so much as the “prospect of a nuclear weapon going off in Manhattan,” various media reported.

And Mr. Trump’s response?

That’s just “one of the dumbest statements” to ever be spoken by a president, he told Greta van Susteren on her Fox News show on Wednesday evening.