Iran on August 6 asked the UN to push back on U.S. sanctions and the Islamic republic's President Hassan Rohani said restrictive measures must be lifted first before negotiations can start about the country's nuclear program.
Tension between the two countries stems from last year when U.S. President Donald Trump withdrew from a 2015 nuclear deal between Tehran and world powers and imposed new and harsher sanctions on Iran's oil and financial sectors.
Iranian state TV showed Rohani meeting with Foreign Minister Mohammad Zarif, who both are on a U.S. sanctions list, while reiterating that the restrictive measures are an act of "economic terrorism."
Meanwhile, Iran's UN Ambassador, Majid Ravanchi, sent a letter of protest to UN Secretary-General Antonio Guterres urging him to "play your active role in preserving the integrity of the United Nations in line with your responsibility to counter the current dangerous trend."
It is not clear how Guterres can act in response and UN spokesman Stephane Dujarric declined to comment on the letter.
Trump has said publicly several times that he is willing to hold talks with the Iranians even as he implements his campaign of "maximum pressure."
Iran recently threatened to block all energy exports out of the Strait of Hormuz, through which a fifth of global oil passes, if it’s unable to sell oil as promised under the 2015 deal, which lifted nuclear-related sanctions as long as Iran's nuclear activities remained peaceful in nature.
U.S. Energy Secretary Rick Perry said on August 6 that the United States and Saudi Arabia had agreed to counter Iran's attempts to "destabilize" the global oil market, according to a read out of his meeting with Saudi Minister of Energy, Industry, and Mineral Resources Khalid al-Falih.
Now Tehran said it no longer feels bound to comply with the nuclear deal.
Iran this week said it had increased its stockpile of heavy water beyond the 130-ton limit, according to Behrouz Kamalvandi, a spokesman for the Atomic Energy Organization of Iran.
Tehran also exceeded the maximum reserve of 300 kilograms of low-enriched uranium.