Iran as rejected any modification of its 2015 nuclear deal with world powers after US President Donald Trump demanded tough new measures to keep the agreement alive.
The Iranian foreign ministry in a statement said that Iran will not accept any amendments in this agreement now or in the future". Foreign Minister Javad Zarif added that the demands were a "desperate attempt" to undermine the deal.
Iran has the backing of all the partners to the agreement apart from the United States, with Russia warning Washington that withdrawing would be "a big miscalculation".
The US President has made a temporary renewal of the agreement. He had previously described it as "the worst deal ever".
Trump said on Friday he would waive nuclear sanctions against Iran for the last time to give Washington and its European allies a chance to fix the "terrible flaws" of the 2015 nuclear deal.