John Bolton, the US national security advisor, has publicly accused Iranian forces armed with naval mines of carrying out an attack on oil tankers earlier this month.
Speaking in the United Arab Emirates (UAE), Mr Bolton said Iran “almost certainly” used mines in the sabotage attack which damaged two oil tankers and two smaller ships at the Emirati port of Fujairah.
“There is no doubt in anybody’s mind in Washington who is responsible for this and I think it’s important that the leadership in Iran know that we know,” he said.
But Mr Bolton also adopted a softer tone than in the past, saying the US was not planning military action in response to the Fujairah attack.
However, he warned and Iran its proxy groups that “that these kind of activities risk a very strong response from the Americans.”
Mr Bolton also said Iran had unsuccessfully tried to carry out an attack at the Saudi port of Yanbu but gave no further details.