President Donald Trump has repeatedly threatened to pull out of the JCPOA unless Congress and America's European allies "fix" it with a follow-up accord.
Also on Wednesday, China urged all sides to stick to the landmark deal that the United States and Israel have threatened to kill.
Iran's foreign minister said Thursday Iran will not renegotiate a 2015 nuclear agreement with world powers.
Trump could refuse to renew the waivers but give new U.S. Secretary of State Mike Pompeo time to negotiate more with the Europeans, exploiting the deal's dispute resolution mechanism or the time before the most draconian sanctions take effect.
"Iran is committed to the nuclear deal but if the USA backs off" from the accord "we won't stay either", Ali Akbar Velayati, adviser to Supreme Leader Ayatollah Ali Khamenei, was quoted by state-run Mehr news agency as saying Thursday.
A U.S. withdrawal from the 2015 Iran nuclear deal could have severe ramifications for political stability in the Middle East.
Benjamin Netanyahu this week, also claimed Iran has been developing a "secret" nuclear weapons programme.
Their ambassador to the UK, Hamid Baeidinejad, told CNN on Wednesday failure for USA compliance "means that there is no deal left".
UN Secretary-General Antonio Guterres has warned of "dangerous times" as US President Donald Trump considers whether to remain in or leave the worldwide deal that seeks to rein in Iran's nuclear weapons programme.
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"If one day there is a better agreement to replace it, it's fine, but we should not scrap it unless we have a good alternative", Guterres said in an interview with the BBC.
During the press conference, he paraded in front of a huge LED screen, showing what he claimed were a half-ton of documents proving that Iran breached the deal.
"I understand the concerns of some countries in relation to the Iranian influence in other countries of the region".
What has the USA said, then?
"I don't know what the USA president will decide on the 12th of May", Macron told reporters while on a visit to Australia.
Iran denies seek to build a nuclear weapon, or ever breaching the 2015 agreement.
Velayati warned against any attempts to renegotiate in exchange for sanctions relief, saying, "Iran accepts the nuclear agreement as it has been prepared and will not accept adding or removing anything". Analysts and family members of dual nationals and others detained in Iran say hard-liners in the Islamic Republic's security agencies use the prisoners as bargaining chips in negotiations with the West.
Trump gave Britain, France and Germany a May 12 deadline to fix what he views as the deal's flaws - its failure to address Iran's ballistic missile program, the terms by which inspectors visit suspect Iranian sites, and "sunset" clauses under which some of its terms expire - or he will reimpose US sanctions.
Velayati warned against any move to try to renegotiate the 2015 deal.
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The Labour opposition, which now holds a majority in the House of Lords , supported the amendment. Labour claims the amendment would ensure Britain does not crash out of the block without a deal.