President Donald Trump threatened Iran Tuesday with “obliteration” if it attacked any American targets in the future.

“Any attack by Iran on anything American will be met with great and overwhelming force,” Trump wrote on Twitter. “In some areas, overwhelming will mean obliteration.”

The president set a crucial red line for Iran after President Hassan Rouhani said the Trump administration was “afflicted by mental retardation” for implementing additional sanctions on the regime.

“Iran’s very ignorant and insulting statement, put out today, only shows that they do not understand reality,” Trump responded.

Trump said the only thing Iran’s leadership understood was “strength and power” reminding them that the United States had the most powerful military in the world.

He also extended sympathy for the Iranian people.

“The wonderful Iranian people are suffering, and for no reason at all. Their leadership spends all of its money on Terror, and little on anything else,” he wrote.

Trump reminded both Americans and Iranians that the relaxed policies under the previous administration had changed.

“No more John Kerry & Obama!” he wrote.