WASHINGTON: US Vice President Mike Pence in an interview airing Sunday warned Iran "not to test the resolve" of the Donald Trump administration, days after Washington slapped new sanctions on Tehran following a ballistic missile test launch.

Relations between the two sides have deteriorated sharply since Trump took office last month promising a tough line on what he sees as Iranian belligerence toward US interests. "Iran would do well to look at the calendar and realize there's a new president in the Oval Office. And Iran would do well not to test the resolve of this new president," Pence said.

The tough talk came after Trump's Pentagon chief James Mattis declared last week that Iran was "the single biggest state sponsor of terrorism in the world."

"The Iranians got a deal from the international community that again, the president and I and our administration think was a terrible deal," Pence said.

Although Mattis and Secretary of State Rex Tillerson have said the United States would stand by the agreement, Pence was less forthcoming. "Well, we're evaluating that as we speak," he said. "I think the president will make that decision in the days ahead. And he'll listen to all of his advisors, but make no mistake about it. The resolve of this president is such that Iran would do well to think twice about their continued hostile and belligerent actions."