(CNN) -

Iranian President Hassan Rouhani on Saturday called new U.S. penalties against firms violating sanctions against Iran illegal and a crime against humanity, the official Islamic Republic News Agency reported.

"We should resist such an aggression with all might and power," Rouhani said at a news conference in Tehran, according to the news agency. "We consider some of the sanctions crimes against humanity. Definitely, we will resist any sanction."

His remarks come one day after the United States imposed new penalties against more than 30 individuals and companies, including banks, accused of providing U.S. dollar banknotes to Iran, supporters of Iran's missile and nuclear programs and sellers of Iranian oil, according to a U.S. officials.

Several overseas airlines also were targeted for allegedly ferrying weapons and personnel to Syria in support of the Assad regime there.

A senior U.S. administration official said the actions were meant to demonstrate that the U.S. and partner countries were active in ongoing negotiations over Iran's nuclear program and will aggressively enforce existing sanctions.

"The message that we have conveyed has been very clear, which is that Iran can only obtain the sanctions relief, the comprehensive sanctions relief that it so desperately needs, by addressing the concerns with its nuclear program at the negotiating table," the senior administration official said.

In a statement, National Security Council spokeswoman Caitlin Hayden said the additional sanctions were aimed at "several companies and individuals engaged in activities such as assistance to Iran's nuclear program, support for terrorism, or aiding Iran's evasion of international sanctions."

"Just as we announced these measures and continue to enforce pre-existing sanctions on Iran, the United States remains committed to working with our P5+1 partners toward a long-term, comprehensive solution that provides confidence that Iran's nuclear program is exclusively peaceful," Hayden said.

Iran and the group known as the P5+1 last month agreed to a four-month extension of negotiations toward a final comprehensive nuclear deal. The P5+1 includes Germany and the permanent members of the U.N. Security Council: the United States, Russia, China, France and Britain.

In January, Rouhani said sanctions against Iran were illegal and undermined international law.