The United Nations and global powers expressed concern on Monday over Iran’s breach of the uranium enrichment limit set by the 2015 nuclear deal. Iran warned on Monday world powers that it will not offer any further "deadlines" to save the nuclear deal by September as it threatened to restart deactivated centrifuges and sharply step up its enrichment of uranium to 20 percent purity. Iran’s main demand - in talks with the European parties to the deal and as a precondition to any talks with the United States - is to be allowed to sell its oil at the levels before Washington pulled out of the agreement and restored sanctions. The UNs atomic energy watchdog confirmed that Iran is enriching uranium above the threshold set in the nuclear accord. The International Atomic Energy Agency said its inspectors verified Monday "that Iran is enriching uranium above 3.67%." The US is open to talks but will keep up pressure on Tehran and will "never allow Iran to obtain a nuclear weapon," Vice President Mike Pence said from Washington He said that "America will not back down," although Pence did not use that phrase when he delivered his speech. He did say that Iran should not "confuse American restraint with a lack of American resolve." The UN said Secretary-General Antonio Guterres believes Irans uranium enrichment breach, if confirmed, would neither help preserve the nuclear agreement "nor secure tangible economic benefits for the Iranian people." UN deputy spokesman Farhan Haq said Monday that the secretary-general encourages Iran to continue implementing all its nuclear commitments under the deal "as the participants continue to seek ways to overcome the considerable challenges the country faces." French President Emmanuel Macrons top diplomatic advisor will travel to Iran on Tuesday and Wednesday to try to de-escalate tensions between Tehran and the United States, a presidential official said on Monday. The French official said both Iran and the United States had an interest in raising pressure at this stage, but that both sides would want to start talks eventually. "The important thing in a crisis situation such as this one is to find the middle points that take us from extreme tension to negotiation, thats what were trying to do," the official said. Israeli Prime Minister Benjamin Netanyahu called on world powers to escalate pressure on Iran in response to its breaching of the nuclear deal. Netanyahu accused Tehran on Monday of "trying to lash out to reduce the pressure." He cited a string of suspected Iranian attacks on oil tankers and its downing of a US drone last month. "Its important to respond to these actions not by reducing the pressure, but by increasing the pressure,” he stressed, urging Europe to back the Trump administrations decision to impose crippling sanctions on Iran. In Moscow, a Kremlin spokesman said Russia is concerned about growing tensions between Tehran and the US. Dmitry Peskov told reporters on Monday that Russia is concerned by Irans announcement it is raising its uranium enrichment levels. He said the Kremlin had warned that Trumps decision to withdraw the US from the nuclear pact a year ago would entail negative consequences to global security. He called on all parties to use diplomacy to overcome the crisis. China expressed regret over Irans violation of the nuclear deal, saying "maximum pressure" from the Trump administration is behind the crisis. Foreign Ministry spokesman Geng Shuang described the comprehensive agreement as the only realistic and effective way to resolve the Iranian nuclear issue and ease tensions, calling for diplomacy to resolve the crisis.