A Twitter account Iran experts believe is run by the office of Supreme Leader Ayatollah Ali Khamenei said on Tuesday "arrogant" powers had tried hard to bring the Islamic Republic to its knees but had failed.In a comment apparently referring to the failure of Iran and six world powers on Monday to end a 12-year dispute about Iran's nuclear goals, a message on the English-language account said: "In the nuclear issue, arrogants have made their best to bring Iran to its knees but they were not able and will not be able to do so."Iranian President Hassan Rouhani took a more conciliatory tone in relation to the talks, saying Monday that the positions of Tehran and six major powers over its nuclear program had come closer after a week of marathon talks that failed to clinch a final agreement."During the talks in Vienna many gaps were narrowed and our positions with the other side got closer," Rouhani told Iranian state television.Iran and the six major powers - the United States, France, Britain, China, Russia and Germany - decided on Monday to extend the talks until June 30, 2015, hoping to finally end the 12-year dispute at a time when Middle East turmoil is worsening."I am certain that we will reach the final accord, if not today, then tomorrow," said Rouhani, who won the Iranian election in a landslide last year promising to ease tension with the West and improve Iran's sanction-hit economy."We have had some agreements behind the scenes, but putting those on paper, we are still not there yet."The goal is a deal that could defuse wider conflict in the Middle East, open the door to ending economic sanctions on Iran and start bringing a nation of 76 million people in from the cold after decades of antagonism with the West.While US Secretary of State John Kerry cited substantial progress, he said that talks would not continue forever and that the coming months would be tough despite new ideas being floated. He did not outline what those ideas were.Publicly all sides say it is still possible to reach a comprehensive agreement that would lift sanctions in return for long-term limits on Iran's nuclear program to ensure it never makes an atomic weapon.Kerry said there would be no additional sanctions relief beyond what was already agreed under an interim deal signed exactly one year ago in Geneva."We not only keep to the Geneva agreement but use the Geneva agreement for coming to a final accord," Rouhani said.While denying it seeks to make nuclear weapons, Iran has refused to halt its enrichment of uranium, prompting crippling US, EU and UN sanctions that have cut deeply into Iranian oil revenues and caused inflation and unemployment to soar."I promise the Iranian people that the centrifuges (enrichment machines) will not stop spinning, but ... people's lives must continue to get better day by day," Rouhani said.