President Trump’s surprise threat to impose new tariffs on Mexico over immigration underscored that he has been a disruptive force not just to U.S. trade policy but to his own trade negotiating team.

“Trump’s approach makes the job of the people in his administration a lot more difficult,” said Simon Lester, a trade policy analyst with the free market Cato Institute. “The foreign officials they are negotiating with must be raising questions about whether what is agreed to will actually be supported by Trump.”