President Donald Trump will announce additional sanctions on Iran's powerful Islamic Revolutionary Guard Corps on Friday, but will stop short of declaring them a terrorist organization.

"We have considered that there are particular risks and complexities to designating an entire army, so to speak, of a country," Secretary of State Rex Tillerson said.

Instead, he said, there will be sanctions "getting at the financing structures themselves and getting at certain individuals, and penalizing people who are supporting these kinds of activities."