“Subjecting construction workers to #EconomicTerrorism only manifests maximum failure of maximum pressure,” Zarif tweeted.

“US can sanction every man, woman & child but Iranians will never submit to bullying,” he added.

The top diplomat urged the US administration to stop its “failed policies” and return to the 2015 nuclear deal with Iran.

The United States said on Thursday it had imposed sanctions on the Iranian construction sector and trade in four materials used in its military or nuclear programs, even as it waived other restrictions to let foreign firms continue nuclear work in Iran.

The US State Department issued a fact sheet, singling out the sale of software used for industrial purposes, raw and semi-finished metals, graphite and coal used in Iran’s construction sector as targets for the new sanctions.

President Donald Trump’s administration last year pulled out of the nuclear deal in which Iran agreed to limit its nuclear program in return for the lifting of sanctions that affected its economy.

The administration has since restored and tightened US sanctions to try to force Iran to negotiate a broader deal that would also limit its ballistic missile program and regional influence.

The State Department said Secretary of State Mike Pompeo had determined Iran’s construction sector was controlled directly or indirectly by Iran’s Islamic Revolution Guard Corps (IRGC).

The US had previously imposed sanctions on a number of Iranian business companies and networks under the pretext of being tied to the IRGC after blacklisting it as a “terrorist” organization earlier this year. The IRGC is an official branch of the Iranian armed forces.

Also on Thursday, the State Department announced a separate batch of sanctions against what it described as the sale of “strategic material” being used “in connection with Iran’s nuclear, military, or ballistic missile programs.”

The State Department listed the sanctioned material as “stainless steel 304L tubes, MN40 manganese brazing foil, MN70 manganese brazing foil, and stainless steel CrNi60WTi ESR + VAR.”

The embargoes mark the latest round of Washington’s sweeping sanctions against Iran after the US government unilaterally pulled out of the 2015 nuclear deal and reimposed sanctions lifted under the agreement last year.

The US has imposed a number of additional embargoes since.

Waiver renewal

Reuters reported on Wednesday that the United States planned to allow Russian, Chinese and European companies to continue work at Iranian nuclear facilities to make it harder for Iran to develop a nuclear weapon.

The Trump administration would let the work go forward by issuing waivers to sanctions that bar non-US firms from dealing with the Atomic Energy Organization of Iran (AEOI).

A source familiar with the matter said on Thursday that the State Department had indeed renewed the waivers for 90 days.

The work to continue includes redesigning Iran’s heavy water Arak research reactor under normal operation and modification of centrifuges at Iran’s Fordo fuel enrichment plant, the source said.

The waivers also cover support for Iran’s existing nuclear reactor at Bushehr, the provision of enriched uranium for the Tehran Research Reactor and the transfer of spent and scrap nuclear fuel out of Iran, the source added.

Chinese state-owned China National Nuclear Corp has done non-proliferation work at Arak, and Russia’s Rosatom has done it at Fordo as well as provided uranium fuel to Iran.

Responding to Reuters’ story that the waivers were to be renewed, a China National Nuclear Corp spokesman said by email that it was “starting to cooperate with the Iranian side under guidance from Beijing on seeking a positive solution to the Iran nuclear problem.”

When Trump abandoned the 2015 nuclear deal last year, he began a “maximum pressure” campaign designed to force Iran to return to the negotiating table.

Iran has demanded the United States first resume complying with the 2015 deal.

France has sought to bring the two into talks but has so far failed, suggesting neither is willing to abandon core elements of policy – the US belief that pressure will bring Iran to its knees, and Iran’s refusal to capitulate to US duress.