The new leader of Iran’s top security body has warned its neighbours against joining new US efforts to squeeze Tehran’s economy, and threatened US commercial interests in the region, as Donald Trump doubled down on his fanciful view that the strait of Hormuz was a new US territory.

Mohsen Rezaei, the hardline new leader of Iran’s supreme national security council, told state television that Iran would target oil-shipping routes out the Gulf – alternatives to the strait of Hormuz – if its neighbours joined what he called the “economic war” waged by the US. Those neighbours would be “considered an enemy” and “we will target their interests”, he said.

Rezaei was a commander-in-chief of the Islamic Revolutionary Guard Corps (IRGC) for most of the 1980-88 war with Iraq and was named this month in a series of senior appointments widely seen as hardening Tehran’s political and military stance.

His interview with broadcaster IRIB is his most extensive public statement since his appointment.

Rezaei also claimed the Islamic republic had more cards to play in the war, saying “we have not yet attacked any American economic interests”.

“So far, we have only targeted military bases, but if they want to impose economic sanctions on us, the United States has oil and economic companies around Iran and elsewhere, and we will strike them,” Rezai said in the interview, broadcast on Saturday.

Last week, Trump announced a new campaign to isolate Iran’s economy, threatening “tremendous economic consequences” on any country that helps or does business with Tehran, as the US president’s unpopular war drags toward the six-month mark without any significant sign of resolution.

Trump’s efforts to finish the war he started along with Israel on 28 February have foundered after a ceasefire agreement signed in June collapsed – leaving Iran in control of the strait of Hormuz, a waterway that was the conduit for one-fifth of the world’s oil supplies before the conflict.

Washington has called on other governments to join its efforts to isolate the Iranian economy, notably China, among Iran’s top strategic partners. However Beijing has criticised the initiative, arguing that US sanctions would not resolve the conflict in the Middle East.

One of Iran’s major trading partners, the United Arab Emirates, announced on Tuesday last week that it was suspending all trade and financial transactions with Tehran until further notice.

The US treasury has for months been carrying out Operation Economic Fury, aiming to cut off Iran’s funding with targeted sanctions, while a naval blockade in the strait of Hormuz has sought to block Iranian ports from exporting oil vital to keeping the country’s economy afloat.

The US president has in recent days repeatedly raised the concept of declaring the strait a US territory. “We control it with the blockade, and I like the idea of declaring it a territory,” he told reporters on Monday when asked about that comment.

On Friday, the US president told a crowd in South Carolina: “We don’t even know if we won, because I view the strait of Hormuz as an American territory right now.”

On Saturday night, Trump again shared on his social media platform a map graphic showing the Gulf and describing the strait of Hormuz as a “new US territory”.

Rezaei said in his interview that discussions continued with cross-strait neighbour Oman over management of the waterway, and said fees would be imposed.

French president Emmanuel Macron and Saudi crown prince Mohammed bin Salman are expected to discuss plans to develop alternative routes to the strait of Hormuz during the Saudi leader’s two-day visit to Paris that starts on Sunday, according to officials in the presidency who weren’t authorised to speak publicly.

Proposals include increasing trade through Omani ports outside the Gulf, expanding or doubling pipelines in Saudi Arabia and elsewhere, and developing new rail links, the officials said.

France and Saudi Arabia have formed a taskforce on energy and logistics connections between the Middle East and Europe that is scheduled to meet at the ministerial level on Monday. The officials said the work would focus on identifying the most strategic projects, securing financing and establishing roles for French companies.

With Associated Press and Agence France-Presse