Iranian President Hassan Rouhani announced on Monday that Tehran may remain in the nuclear deal even if the United States decides to withdraw.
"Either what we want from the nuclear deal is guaranteed by the non-American parties, or it is not the case and we will follow our own path," Rouhani said on the presidency website, without elaborating.
US President Donald Trump is due to announce on Saturday whether the United States will remain in the 2015 deal that lifted international sanctions in exchange for curbs to Iran's nuclear program.
The other parties -- Britain, China, France, Germany and Russia -- have urged Trump to stay in the deal.
Rouhani said on Sunday that the United States would regret "like never before" pulling out of the deal, but has remained vague on how exactly Iran would respond.
On Monday, Rouhani said Iran had "thought of all the scenarios and have taken appropriate measures.
"The United States will be the principle loser in this affair," said Rouhani.
Trump has demanded the Europeans find a way to "fix" the existing deal by putting new curbs on Iran's missile program and regional interventions, or he will reimpose nuclear-related sanctions at the next deadline for review on May 12.
Later on Monday, Boris Johnson appealed once more to Trump not to scrap the nuclear deal, saying that while the president has a "legitimate point" over "flaws" in the accord, the global community has no better alternative.
Speaking to US network Fox News ahead of meetings in Washington with US administration officials, the British Foreign Secretary said Trump was "right to see flaws" in the deal but "Plan B does not seem to be to me particularly well-developed at this stage."
Earlier, German Foreign Minister Heiko Maas warned that the accord's collapse could spark "an escalation" in the region and stressed that Washington's key European allies remain convinced saving it "makes the world a safer place".
His French counterpart Jean-Yves Le Drian, on a Berlin visit, said that the agreement is "the right way to stop Iran from getting access to nuclear weapons" and "will save us from nuclear proliferation".
