A Nasa image showing the Strait of Hormuz taken from the International Space Station. Image Credit: Nasa

Washington: The United States is closely monitoring Iranian naval activity to ensure no disruptions occur to global shipping, a top US general said Wednesday, as tensions with Tehran intensify over renewed economic pressure from the Trump administration.

Gen. Joseph Votel, head of US Central Command, said a recent Iranian naval exercise appeared to be linked to the Trump’s decision to reimpose trade sanctions in the wake of the US exit from the 2015 nuclear deal.

“We are paying attention,” Votel told reporters at the Pentagon.

“We’re extraordinary vigilant and watching for changes in the environment.”

The two countries have exchanged a series of threats in recent weeks, including President Donald Trump’s suggestion that the United States might use military force against Iran to inflict “consequences the likes of which few throughout history have ever suffered before.”

Days later, Iran hit back with a response from Maj. Gen. Qasim Sulaimani, head of the Revolutionary Guard’s Quds Force, who said the US would regret undertaking any military conflict with Iran.

“You may begin the war, but it will be us who will end it,” he said.

Iranian officials have also suggested they could move to shut down the Strait of Hormuz, which serves as transit point for a third of global oil shipments.

US administration officials have vowed to take a tough line on Iran and its support for armed groups across the Middle East, from Lebanon to Iraq to Yemen.

While it has slapped new sanctions on some Iranian affiliates, the administration has yet to curb Tehran’s ballistic missile programme or make visible progress in reducing its proxy activity.

The United States also blames Iran for backing Al Houthi militants in Yemen, who have attacked ships in nearby waters.

Votel singled out Sulaimani for driving much of that militant activity.

He said military officials would use intelligence and surveillance to keep apprised of Iranian activities that might impact maritime commerce.

He also said that since the latest sanctions, Iran had not shown any signs of harassing US ships, as it has done intermittently in the past.

The sanctions imposed this month prohibit Iran from using US dollars, the primary currency for international financial transactions and oil purchases, and restrict Iranian trade in metals, carpets and other goods.