The United States says it has extended five sanction waivers that will allow Russian, China, and European countries to continue to work with Iran's civilian nuclear program.
However, according to a separate statement issued by State Department spokesperson Morgan Ortagus, "starting May 4, assistance to expand Iran's Bushehr Nuclear Power Plant beyond the existing reactor unit could be sanctionable".
Iran says it will continue uranium enrichment and heavy water production despite USA pressure on the country to end it.
Washington acted on Friday to force Iran to stop producing low-enriched uranium and expanding its only nuclear power plant, intensifying a campaign aimed at halting Tehran's ballistic missile program and curbing its regional power.
Efforts by the Trump administration to impose political and economic isolation on Tehran began with last year's United States withdrawal from the nuclear deal it and other world powers negotiated with Iran in 2015.
The Europeans reminded Washington that the Iran nuclear agreement, officially called the Joint Comprehensive Plan of Action (JCPoA) remains a "crucial element" of the global nuclear non-proliferation regime and therefore is "essential" to European security. "We also note with concern the decision by the United States not to fully renew waivers for nuclear non-proliferation projects", Britain's foreign office added.
Besides, Iran would no longer be able to ship additional heavy water produced at its Arak facility to Oman for storage. Iranian President Hassan Rouhani reiterated his country's commitment to the deal, saying Teheran will continue to implement its liabilities.
Under the 2015 deal, which was negotiated under former President Barack Obama and still enjoys strong support among European powers, Iran was limited to keeping 300 kg of uranium enriched up to 3.67 percent - far below the level needed to build nuclear weapons.
"America is trying to decrease our foreign reserves".
Friday's USA move, which Mr Rouhani made no direct reference to, was the third punitive action Washington has taken against Iran in as many weeks.
On April 22, Secretary of State Mike Pompeo said that the US sanctions will be reimposed on all countries that import oil from Iran since May 2.
After Washington re-imposed sanctions on Tehran in November past year, the U.S. government granted eight countries six-months waivers to keep buying Iranian crude.