The prime minister's latest warning to the Islamic Republic comes at a time of heightened tension between the US - Israel's only major ally - and its arch-foe Iran.
British Royal Marines impounded the tanker on suspicion it was carrying oil to Syria in violation of European Union sanctions, a claim Iran denied.
"We are extremely concerned at Iran's announcement that it has started uranium enrichment above the limit of 3.67%", Maja Kocijancic said.
He confirmed that "we surpassed the %3.67 limit". If the Europeans "do certain odd acts, then we would skip all the next steps (in the plan to scale back commitments) and implement the last one", he said.
"Iran has violated its solemn promise under the UN Security Council not to enrich uranium beyond a certain level", he said.
"If Iran attacks the United States, they're gonna get a response that will be strong and definitive", Rubio said.
Deputy Foreign Minister Abbas Araghchi said Sunday that Iran would cross another of the deal's lines in 60 days, saying, "This is an opportunity for talks".
US Secretary of State Mike Pompeo had tweeted on Sunday that Iran would face "further isolation and sanctions".
Russian Federation said it is concerned about the Iranian action, but Kremlin spokesman Dmitry Peskov said it had warned that Trump's withdrawal from the pact would have negative consequences for global security.
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Under the deal, Iran agreed to destroy its stockpile of medium-enriched uranium and cut its stockpile of low-enriched uranium by 98%.
It is considered an important intermediate stage on the path to obtaining the 90% pure fissile uranium needed for a bomb.
He adds, according to a partial transcript published Netanyahu's office, that "it's a awful deal because it gave Iran a path to getting a nuclear arsenal when the restrictions on Iran's nuclear programs were removed". Iran has the technical ability to build and operate advanced centrifuges that work faster, but is barred from doing so under the deal.
Still, the threatened measures also appear meant to be sufficiently ambiguous to hold back from fully repudiating the deal.
The accord between Iran and world powers promised sanctions relief, economic benefits and an end to worldwide isolation of the Islamic republic in return for stringent curbs on its nuclear programme. Iran has said all the steps it is contemplating are reversible.
"The doors of diplomacy are open but what matters are new initiatives which are required".
French Foreign Minister Jean-Yves Le Drian says the US can help encourage dialogue with Iran to ease growing tensions even though it withdrew from the 2015 nuclear accord with Iran.
European countries do not directly support the USA sanctions, but have been unable to come up with ways to allow Iran to avert them.
French President Emmanuel Macron condemned Iran's decision as a "violation" of the pact which the United States pulled out of previous year.