Iran's foreign minister has rejected as "unacceptable" US President Barack Obama's demand that the Islamic Republic freeze sensitive nuclear activities for at least 10 years as part of a landmark nuclear deal, the country's semi-official Fars news agency reported.
Mohammed Javad Zarif reportedly made the remarks as he met with his US counterpart for a second day of negotiations in Switzerland, and as Israeli Prime Minister Benjamin Netanyahu delivered a stinging critique of the agreement they are trying to hammer out.
Obama had made the comments regarding a freeze in an interview with the Reuters news agency on Monday. But Zarif dismissed the demand on Tuesday, according to Fars.
"Iran will not accept excessive and illogical demands," Zarif was quoted as saying.
"Obama's stance ... is expressed in unacceptable and threatening phrases," he was reported as saying, adding that talks with Kerry in Switzerland would nonetheless carry on.
Six world powers - including the five UN Security Council permanent members Britain, China, France, Russia and the US, as well as Germany - have previously held several rounds of talks and have set March as the deadline to agree a deal on the way forward.
The US and some of its allies, notably Israel, suspect Iran of using its civil nuclear programme as a cover to develop a nuclear weapons capability. Iran denies this, saying it is for peaceful purposes such as generating electricity.
Addressing the US Congress on Tuesday, Netanyahu warned Obama against accepting a nuclear deal with Iran that would be a "countdown to a potential nuclear nightmare" by a country that "will always be an enemy of America".
"If the deal now being negotiated is accepted by Iran, that deal will not prevent Iran from developing nuclear weapons - it will all but guarantee that Iran will get those nuclear weapons, lots of them," the Israeli leader said in a 39-minute point-by-point critique of Obama's Iran diplomacy.
In a similar speech in 2012, Netanyahu warned the UN General Assembly that Iran was 70 percent of the way to completing its "plans to build a nuclear weapon".
However, a secret cable obtained by Al Jazeera's Investigative Unit revealed last month that at the time of the UN speech Mossad - Israel's intelligence service - believed that Iran was "not performing the activity necessary to produce weapons".
Obama said Netanyahu had on Tuesday offered no "viable alternatives" in his speech for dealing with Tehran and urged Congress to withhold judgement until an agreement with Iran had been finalised.
The president said he would only agree to a deal that prevents Iran from obtaining a nuclear weapon.
Kerry and Zarif met for more than five hours on Tuesday in the Swiss lakeside town of Montreux, negotiating during most of Netanyahu's extended criticism of their efforts in Washington.
Netanyahu wants the Iranians stripped of nuclear projects that might be used to get a bomb. Washington deems the Israeli demand unrealistic.