US Defense Secretary James Mattis has called Iran the world's biggest state sponsor of "terrorism", hours after the Trump administration announced fresh sanctions on the country following a recent missile test.
"As far as Iran goes, this is the single biggest state sponsor of terrorism in the world," Mattis told reporters in Tokyo on Friday, before adding that he saw no need to increase troop numbers in the Middle East in response.
"I don't see any need to increase the number of forces we have in the Middle East at this time. That's not in the cards right now," he said.
"We always have the capability to do so. But right now I don't think it's necessary."
Last Sunday, Iran test-fired a medium-range missile, which the White House says violated a UN Security Council resolution proscribing missiles that could carry a nuclear device.
Tehran has confirmed it tested a ballistic missile but has denied it was a breach of a 2015 nuclear deal.
Mattis said ignoring Iran's actions - something President Donald Trump routinely accused former President Barack Obama of doing - would not work.
"It does no good to ignore it, it does no good to dismiss it," Mattis said, without citing Obama or his policies.
In a post on Twitter, Trump said he would not be as "kind" to Iran as the government of his predecessor.
Earlier on Friday, the US Treasury said it added 13 Iranians and 12 companies, some of which are based in Lebanon, the United Arab Emirates and China, to its sanctions list after the recent missile test.
Among those targeted was Iranian businessman Abdollah Asgharzadeh whom the Treasury accused of acting as a procurement agent for the ballistic missile programme.
US officials added that while the latest sanctions were a reaction to recent events, they had been under consideration before.
Trump has vowed a more aggressive policy against Tehran and has made no secret of his contempt for that the nuclear deal that Obama approved in July 2015.
Iran denounced the sanctions as "illegitimate" and said it would impose its own legal restrictions on American individuals and entities helping "regional terrorist groups", according to a foreign ministry statement quoted by state TV.
Al Jazeera's Dorsa Jabbari, reporting from Tehran, said the "list of individuals and entities will be released by the Iranian foreign ministry after it decides who will make the cut".
In another development, Iran said it would deploy missiles for a Revolutionary Guards exercise on Saturday in a show of defiance.
The Guards' Sepahnews website said the manoeuvres were aimed at demonstrating their "complete preparedness to deal with the threats" and "humiliating sanctions" from Washington.
Source: Al Jazeera and news agencies