Hillary Clinton has warned America might cope with a nuclear Iran by arming US allies in the Gulf and extending a "defence umbrella" over the region.
US Secretary of State said crossing the nuclear threshold would not make Tehran, which Washington believes is pursuing nuclear weapons, safer or more secure.
Iran has insisted its nuclear programme is to generate electricity so it can export more oil and gas.
Mrs Clinton said: "We will still hold the door open (for talks with Iran) but we also have made it clear that we'll take actions... crippling action, working to upgrade the defence of our partners in the region.
