Iran says it will not accept any change to the nuclear deal it struck with the US and other powers.
The statement was a response to President Trump's demand on Friday for a follow-on agreement that would impose new restrictions on Tehran.
US president Donald Trump vowed to pull out of the accord if European allies do not fix its "terrible flaws".
Other signatories to the agreement -- including Britain and France - believe it's working, and Russia has described Mr Trump's remarks as
The Iranian foreign ministry said it "will not accept any change in the deal, neither now nor in future", adding that it will "not take any action beyond its commitments".
On Friday, Mr Trump extended the waivers of key economic sanctions that were lifted under the agreement limiting Iran's nuclear programme.
However, he said he would work with European allies to remove so-called "sunset clauses" that allow Iran to gradually resume advanced nuclear activities in the next decade.