Iranian President Hassan Rohani said on Monday that American pressure on Iran in the middle of the coronavirus pandemic was "inhumane", according to a statement on the official presidency website.
Iran is the Middle Eastern country hardest hit by the virus and Iranian officials say U.S. sanctions have hampered its response.
U.S. President Donald Trump reimposed economic sanctions on Iran in 2018 after withdrawing from a multilateral nuclear deal struck three years earlier.
"In these difficult conditions, American pressure on the people of Iran is more inhumane than at any other time and the continuation of it is a barbaric crime against a great people and against all human principles and international regulations," Rohani said during a phone call with Italian Prime Minister Giuseppe Conte.
Rohani expressed sympathy for the people of Italy, who have also been hit hard by the coronavirus outbreak.
Trump says the multilateral deal was not strong enough to ensure that Iran would not be able to develop and build nuclear weapons.
He wants to apply "maximum pressure" on Iran to accept tougher curbs to its nuclear programme, halt its ballistic missile work and end its support for proxy forces in the Middle East. Iran says it will not negotiate unless Washington lifts sanctions.
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France, Germany and Britain have exported medical goods to Iran in the first transaction conducted under Instex, a trade mechanism set up to barter humanitarian goods and food with Iran in the hope of encouraging it to remain committed to the nuclear deal.
But Rohani said Instex had not been sufficient so far.
"The financial mechanism designed by Europe unfortunately has not been able to take a noticeable and effective step and play a role," he said, according to the presidency website.
Separately, in a phone call with Kuwaiti Emir Sheikh Sabah al-Ahmad al-Sabah, one of several Sunni-ruled Arab Gulf states that are at odds with Iran, he said that, to achieve security in the region, "there is no other way other than cooperation and friendship between the countries of the region itself".