Stalled nuclear talks between the EU, Iran and, indirectly, the United States, suffered a double blow on Wednesday when two thirds of the governing body of the International Atomic Energy Agency (IAEA) — the UN’s nuclear watchdog — expressed “strong concern” about unexplained nuclear activity at four sites in the country. In a separate development, the EU foreign policy chief Josep Borell said on Wednesday that he did not have “anything more to propose", to move negotiations forward, a week after Iran again said it was stepping up uranium enrichment, far beyond limits set under a previous 2015-2018 nuclear deal, which the Donald Trump administration scrapped. On Wednesday, US Secretary of State Antony Blinken called Iran's response to an EU draft of a new deal "a step backward". The IAEA has repeatedly asked Iran to explain how “man-made” uranium particles were found at four sites by UN inspectors, places that Iran had said were not used for nuclear research. The IAEA announced in 2016 that unexplained uranium particles had been found at Parchin, a large research complex 30 kilometres south of Tehran, drawing attention to three other sites in subsequent years. Uranium ore contains about 1 per cent of the metal and has to be refined to a high concentration before being used for civilian or military nuclear purposes, hence the IAEA’s term “man-made”. Iran has given the IAEA explanations for the presence of the metal, but the UN’s atomic watchdog has rejected them. The argument is described as the “safeguards issue” because it relates to what the IAEA calls safeguards that should be put in place to ensure Iran does not obtain a nuclear weapon. The IAEA board decision represents a formal decision by the organisation. "We call upon Iran to act immediately to fulfil its legal obligations and, without delay, take up the [IAEA] director general's offer of further engagement to clarify and resolve all outstanding safeguards issues," according to the joint statement presented by Germany to the board. The Vienna-based IAEA says there has been no progress and no engagement by Iran since a previous resolution urging co-operation in June. Rather than pass a new resolution at this week's board meeting, the four countries behind June's resolution ― the US, Britain, France and Germany ― issued a joint statement reaffirming support for that text and sought to get as many other countries as they could to sign up it. A list of countries provided by Germany showed that 23 countries on the board supported it. The 12 that did not included Argentina, Brazil, Mexico, Egypt, South Africa, India, Pakistan, Malaysia, Senegal and Vietnam. Amid the safeguards impasse, negotiations had reached a stalemate, Mr Borrell told AFP on Wednesday. "I am afraid that with the political situation in the US, and so many directions without being conclusive, now we are going to stay in a kind of stalemate," Mr Borrell said. Mr Borrell has co-ordinated efforts over the past year and a half to try to revive the 2015 Iran nuclear deal. Iran has responded by rolling back its adherence to its commitments, greatly increasing its stock of enriched uranium and turning off monitoring cameras operated by the IAEA. Last month, Mr Borrell put a text in front of all parties that he described at the time as final and which he told AFP on Wednesday was "the best equilibrium point between the positions of everybody". But Iran is sticking to a demand that the IAEA draw a line under an investigation launched when the agency found traces of nuclear material at three undeclared sites. Meanwhile, the US political situation has changed as President Joe Biden faces midterm Congressional elections in November that make deals with Iran harder to reach. Mr Borrell said that, over the past couple of months, "the proposals were converging but unhappily, after the summer, the last proposals are not converging ― they are diverging". "The last proposals from the Iranians were not helping because we were almost there, then new proposals came and the political environment is not the most propitious. I am sorry to say, but I don't expect any breakthrough in the next days." he said. The European parties to the nuclear deal, Britain, France and Germany, last week said they had "serious doubts" about Iran's sincerity in wanting the pact restored. Iran called the joint declaration "unconstructive" and "regrettable".