The U.S. government has extended for another 60 days sanction waivers that allow Russian, Chinese, and European countries to continue nonproliferation work at Iranian nuclear sites.
Secretary of State Mike Pompeo approved the waiver extensions on March 30 but maintained that the decision restricts Iran's atomic work.
"Iran's continued expansion of nuclear activities is unacceptable. The regime's nuclear extortion is among the greatest threats to international peace and security," State Department spokeswoman Morgan Ortagus said in a statement.
President Donald Trump's unilateral withdrawal in 2018 from a landmark nuclear deal with Iran that included signatories Britain, Germany, France, Russia, and China, saw U.S. sanctions reimposed on Tehran, crippling its economy, which is mostly reliant on oil exports.
The deal, brokered in 2015, envisioned sanctions relief if Iran curbed its nuclear ambitions.
Since withdrawing from the deal, Washington has pursued a "maximum pressure" campaign aimed at reducing Iran’s regional activities and limiting its nuclear missile program.
The waivers allow nonproliferation work to continue at the Arak heavy-water research reactor, the Bushehr nuclear power plant, the Tehran Research Reactor, and other nuclear initiatives.
The United States will continue to closely monitor all developments in Iran’s nuclear program and can adjust the restrictions at any time, Ortagus said.
"As President Trump said earlier this year, Iran will never be allowed to have a nuclear weapon," she said.
Earlier this month, the International Atomic Energy Agency (IAEA) said that Iran had been blocking international nuclear inspectors from investigating possible nuclear activities at two sites.
The Vienna-based agency also said Tehran had exceeded its uranium stockpiles beyond the limits set by the 2015 nuclear deal.
Iranian authorities have blamed Washington’s policies and sanctions for hampering its ability to cope with the coronavirus pandemic.
More than 41,000 confirmed COVID-19 cases have been recorded, including over 2,700 attributable deaths, according to a tracking monitor by the U.S.-based Johns Hopkins University.
Iran is one of the countries worst hit by the virus, and experts have been skeptical about the veracity of official figures released by the Islamic regime, which keeps a tight lid on local and foreign media.