US President Donald Trump said on Sunday Ukrainian President Volodymyr Zelenskyy wants to back out of a critical minerals deal, Reuters reports.

Also, the White House chief warned the Ukrainian leader would face big problems if he did.

“He's [i.e. Zelenskyy] trying to back out of the rare earth deal and if he does that he’s got some problems, big, big problems,” Trump told reporters aboard Air Force One. “He wants to be a member of NATO, but he's never going to be a member of NATO. He understands that.”