The US is giving plenty of warning ahead of its latest round of sanctions against Iran's shipping industry.

In 180 days — 8 June, 2020 — the Islamic Republic of Iran Shipping Lines will be added to the US Treasury's blacklist, after the company allegedly aided Iran in its development of weapons of mass destruction.

US Secretary of State Mike Pompeo said the company had sanctions lifted under the 2015 nuclear deal scuttled by President Donald Trump last year.

"That was an enormous mistake," Pompeo said Wednesday.

"Since then, that entity has knowingly engaged in activities and transactions that materially contribute to Iran’s proliferation of [weapons of mass destruction]."

Similarly, Shanghai-based ESAIL Shipping Company will be sanctioned 8 June for shipping materials from Iran's Aerospace Industries Organization, which oversees the country's missile industry.

The delay is to give exporters of humanitarian goods time to find alternate shipping methods.

The US also sanctioned businessman Abdolhossein Khedri, two of his companies and two of his ships over alleged illicit weapons shipments to Iran-backed Houthi rebels in Yemen effective immediately.

Authorities allege that Khedri, through companies Khedri Jahan Darya and Maritime Silk Road, used the 499-gt deck cargo vessels Genaveh 11 (built 2017) and the Genaveh 12 (built 2015) to support the Islamic Revolutionary Guards Corps-Quds Force's efforts to arm Yemen's Houthi rebels in their fight against Saudi Arabian-backed forces.

Equasis identifies the Khedri Jahan Darya as owner of the vessels. Maritime Silk Road allegedly chartered the ships.

The US said in November it seized weapons smuggled on a small boat headed for Yemen, but it is unclear if that vessel is either of the ships sanctioned.

The Qods Force is the arm of the Iranian Revolutionary Guard responsible for unconventional warfare and is considered by the US to be a terrorist organisation.

In September, the US hit out at what it called an "oil for terror" network consisting of a dozen companies, six ships and nine individuals stretching from Lebanon to India. The network allegedly funnelled "hundreds of millions of dollars" worth of oil to the Bashar al-Assad regime in Syria and others.

The Iran-aligned, Yemen-based Houthi rebels claimed responsibility for September's bombing of a Saudi Arabian oil facilities. The US immediately said Iran was behind the attack, and was eventually joined by others, but Tehran denied involvement.

Wednesday, the UN said it was unable to independently verify that Iranian weapons were used in the attack.

The sanctions continue what the US has called its "maximum pressure" campaign on Iran, which commenced after withdrawal from the 2015 nuclear deal. The deal was supposed to lift sanctions in exchange for Iran scaling down its nuclear weapons programme.

Withdrawal, and the reimposition of sanctions against the Islamic republic, is largely considered the impetus behind rising tensions around the Middle East Gulf, including two tanker bombings earlier this year.