President Donald Trump and Secretary of State Marco Rubio issued stark warnings to Iran Monday that the "hardest hits" in its new conflict in the region is still to come if it does not agree to end its nuclear program.

The United States and Israel launched missiles at Iran over the weekend, which resulted in the death of Iranian Supreme Leader Ayatollah Ali Khameini. Iran has since retaliated by targeting Israel and U.S. bases in several Middle Eastern countries.

Trump told CNN that he thinks the U.S. side of the conflict is "going very well," and warned Iran that bigger hits could still be coming.

“We’re knocking the crap out of them,” Trump said. “We’ve got the greatest military in the world and we’re using it ... We haven’t even started hitting them hard. The big wave hasn’t even happened. The big one is coming soon.”