Iranian Foreign Minister Mohammad Javad Zarif has said that demands by U.S. President Donald Trump to alter Tehran's nuclear deal with world powers are unacceptable.
Zarif made the remark on April 28 in Moscow, where he is attending talks on the conflict in Syria.
Trump has threatened to pull the United States out of the Iran nuclear deal unless European allies fix its "terrible flaws" by May 12.
The deal provides Tehran with relief from sanctions in return for curbs on its nuclear program, but Trump has said the terms are not strict enough.
Germany, France, Russia, China, and Britain have also signed the accord and have urged Washington to remain a part of the deal, saying it is the best way to prevent Iran from acquiring nuclear weapons.
On April 27, Trump vowed that Iran would not acquire nuclear weapons, but declined to speak about what measures, if any, he would take to deter Iran should the deal collapse.
"I don't talk about whether or not I would use military force," Trump said at a joint news conference with visiting German Chancellor Angela Merkel.
"But I can tell you this -- they will not be doing nuclear weapons. That I can tell you. OK? They are not going to be doing nuclear weapons. You can bank on it. "
Merkel said the accord was "anything but perfect," but she described it as "one building block" and a "first step" that has contributed to slowing down Tehran's nuclear activities.