James Mattis
James MattisReuters

U.S. Defense Secretary James Mattis on Saturday blasted Iran and described it as "the single biggest state sponsor of terrorism in the world".

Iran's "misconduct and misbehavior" would have to be addressed, said Mattis, who spoke a day after the United States imposed new sanctions on Iran in response to its latest ballistic missile test.

"We have a responsibility with the rest of the nations to be absolutely clear with Iran in this regard. It does no good to ignore it. It does no good to dismiss it," Mattis was quoted by CNN as having said in Tokyo, where he met with his Japanese counterpart to discuss security issues.

At the same time, he said the recent tensions with Iran did not warrant an increase in the number of U.S. forces in the Middle East.

"We always have the capability to do so, but at this time I don't think it's necessary," stressed Mattis.

On Friday, the Treasury Department announced new sanctions on 25 individuals and companies connected to Iran's ballistic missile program and those providing support to the Revolutionary Guard Corps' Qods Force.

The sanctions came in response to a ballistic missile test conducted by Iran last week, in violation of UN Resolution 2231, which bars Iran from conducting ballistic missile tests for eight years and which went into effect after the nuclear deal between Iran and the six world powers was signed.

Iran’s Defense Minister, while acknowledging his country fired a ballistic missile this week, claimed the test did not violate the nuclear deal or UN Resolution 2231.

On Saturday, Eshaq Jahangiri, Iran's first vice president, dismissed the remarks from Mattis as "useless claims."

"The Iranian government and nation do not care in the least for the worn-out and threadbare remarks made by the American officials," Jahangiri said, according to CNN.

As Mattis made his comments Saturday, Iran's air force was conducting military drills, including missile systems, radar and electronic warfare command and control exercises, in the northern Semnan province.

Iran's Ministry of Foreign Affairs blasted the American sanctions on Friday, vowing that it too would ensure "legal restrictions" were imposed on the "American individuals and companies which have a role in aiding extremist and terrorist groups or contribute to the suppression and murder of the defenseless people in the region.”