Turkish President Recep Tayyip Erdogan celebrated the delivery of the first S-400 anti-air missiles on Tuesday, even going so far as to suggest that Turkey and Russia (the system is made by Russian defense contractor Almaz-Almaty) might collaborate on building weapons. But across the Atlantic, President Trump was less than amused.

Washington has repeatedly insisted that if Turkey bought the S-400 over a steeply discounted Patriot missile system, that the US would block the sale of Lockheed Martin's F-35 fighter jets - and unprecedented punishment for a NATO member. And as it turns out, that's exactly what President Trump is planning to do.

During a Cabinet meeting on Tuesday, Trump said "we are now telling Turkey...we're not going to sell you the F-35 fighter jets."

Trump added: "It’s a very tough situation that they’re in. And it’s a very tough situation that we’ve been placed in the United States," Trump said. "With all of that being said, we’re working through it. We’ll see what happens, but it’s not really fair."

But Trump was mum on a more pressing issue: Whether Washington will subject Ankara to sanctions under the Countering America’s Adversaries Through Sanctions Act, or CAATSA. While Erdogan has suggested that Trump would find a way to avoid the sanctions, last year, Congress set a high bar for waiving sanctions under CAATSA.

And what's more, if Washington doesn't make an example of Ankara, it could have a full-blown mutiny on its hands, as New Delhi is also eyeing the S-400.

Trump isn't the only senior US official talking tough about the S-400. During his Senate Armed Services Committee confirmation hearing, Esper said that he has told his Turkish counterpart that "you can either have the S-400 or the F-35, you cannot have both."

But who knows? Maybe one one-on-one phone call between Erdogan and Trump will resolve everything.