Iran took “a step backwards” with its latest response to the proposal for a nuclear deal, US Secretary of State Anthony Blinken said on Monday, calling a short-term deal “unlikely”.   

  “What we’ve seen in the last week or so in Iran’s response to the proposal put forward by the European Union is clearly a step backwards and makes the prospects for a deal in the short term, I would say, unlikely,” Blinken said.  reporters, speaking from Mexico City, where he met with Mexican President Andrés Manuel López Obrador.   

  The United States and Iran exchanged responses through the European Union to a proposal made by the EU’s top diplomat, Josep Borrell.  Iran submitted its initial response in mid-August.  the US responded to this about a week later.   

  Earlier this month, Iran sent its latest response, which a State Department spokesman called “not constructive.”   

  As CNN previously reported, according to a senior US administration official, Iran in its latest response reopened the issue of the UN nuclear watchdog’s investigation into undeclared traces of uranium found at Iranian facilities.  Iranian officials have repeatedly said the International Atomic Energy Agency (IAEA) investigation would have to be closed before they could return to the deal.  However, a separate senior US government official suggested last month that Iran had accepted the EU’s proposal – described by Borrell as the “final text” – without any demands on the probe.   

  Blinken said on Monday that he could not provide a time frame for when he believed it would be possible to rejoin an Iran nuclear deal, saying that Iran was either “unwilling or unable to do what is necessary to agreement reached”.   

  “They keep trying to introduce extraneous issues into the negotiation that make a deal less likely,” Blinken said.  “But certainly what we’ve seen in the last week is a step back from the possibility of any kind of short-term deal.”   

  US officials had previously expressed some optimism about the latest efforts to revive the nuclear deal – which the US abandoned in 2018 during the Trump administration and which Tehran has increasingly violated since then – but hopes of significant progress remain to weaken.