Saturday brought new sanctions on Iran's nuclear reactor and power plant complex aimed at blocking the nation's development of nuclear weapons.

"Starting May 4, assistance to expand Iran’s Bushehr Nuclear Power Plant beyond the existing reactor unit will be exposed to sanctions," Secretary of State Mike Pompeo announced late in the evening on Friday.

The tightening on sanctions on Iran's nuclear power complex is meant to curb its ability to refine uranium and mitigate its pursuit of a nuclear weapon. Pompeo said Iran would not be able to return to the negotiating table until it ceases all activities related to, or associated with, the construction of a nuclear weapon.

The new sanctions would mean that any country that assists Iran in its completion of the nuclear power plant will be subject to punitive measures enforced by the U.S. government.

The original Bushehr power plant was designed and built by Russia over a decade ago. Iran is now looking to expand the plant with an additional reactor. It is not clear if Russia is looking to assist in the construction of the project.

The new sanctions would also cover any involvement in transferring enriched uranium out of Iran in exchange for mined uranium from the Islamic Republic.

"The United States has been clear that Iran must stop all proliferation-sensitive activities, including uranium enrichment, and we will not accept actions that support the continuation of such enrichment," Pompeo said in a statement.