When Secretary of State Mike Pompeo announced the Trump administration would designate a branch of Iran's military as a foreign terrorist organization Monday, he said, "The Trump administration is simply recognizing a basic reality."

But critics say they are concerned that it may also be part of an effort to bend reality enough to provide legal justification for armed conflict with Iran.

"I am troubled that the administration can't unequivocally say that you haven't been given power. I can tell you explicitly, you have not been given power or authority by Congress to have war with Iran," Sen. Rand Paul, R-Ky., told Pompeo on Wednesday.

The Trump administration will officially designate Iran's Islamic Revolutionary Guard Corps as a foreign terrorist organization on Monday, making it the first foreign government entity on the State Department list. But the IRGC is already under heavy sanctions through the State and Treasury Departments, including as a Treasury special globally designated terrorist entity.