Ali Akbar Velayati, the Leader's senior advisor on international affairs, made the remarks while speaking to reporters on the sidelines of his visit to Tehran International Book Fair on Sunday, a few days ahead of a May 12 deadline set by US President Donald Trump to either scrap or uphold the multilateral nuclear pact, officially known as the Joint Comprehensive Plan of Action (JCPOA).
President Trump, a long-time critic of the JCPOA, has repeatedly threatened to abrogate the nuclear agreement by not extending sanctions waivers when they expire, if the European signatories to the deal -- Britain, France and Germany -- do not "fix" its "terrible flaws", Presstv Reported.
Velayati said, “If Americans decide to withdraw from the JCPOA, the Islamic Republic of Iran will undoubtedly take measures proportionate to conditions that they want to impose and will make them regret [their decision].”
He added that Iran has an open hand to respond to any decision about the fate of the JCPOA, saying, "The Americans can test this issue."
A senior Iranian lawmaker said on Saturday any violation of the multilateral nuclear deal would further undermine America’s standing in the world.
"Any violation of or threat to violate the JCPOA by the US will practically tarnish the country's international credibility and will prove that the US cannot be trusted in the international scene," Chairman of the Iranian Parliament's Committee on National Security and Foreign Policy Alaeddin Boroujerdi said.
The legislator's comments came after Head of the Atomic Energy Organization of Iran (AEOI) Ali Akbar Salehi also said the country has enough technical know-how to return to conditions it had before signing the JCPOA.
“In terms of nuclear science, Iran has reached a level that if we fail to fulfill those promises that we gave to people upon signing the JCPOA, we will return to the past [conditions] and [even] a much better level [of the nuclear activities],” Salehi told reporters on Monday.
Under the multilateral nuclear agreement, reached under Trump's predecessor Barack Obama, Iran undertook to put limits on its nuclear program in exchange for the removal of nuclear-related sanctions imposed against Tehran.