The United States will not ease sanctions on Iran before a third round of talks between major powers and Iranian officials about Tehran\'s nuclear program, U.S. Secretary of State Hillary Clinton said on Thursday. \"As we lay the groundwork for these talks, we will keep up the pressure as part of our dual-track approach. All of our sanctions will remain in place and continue to move forward during this period,\" she told reporters in Washington hours after talks between Iran and world powers concluded in Baghdad. Iran and world powers agreed to meet again in Moscow on June 18-19 for more negotiations to try to end the long dispute over Tehran\'s nuclear program but there appeared to be scant progress to resolve the main sticking points between the two sides. At the heart of the dispute is US resistance to Iran\'s right to enrich uranium and US wants economic sanctions not to be lifted. A senior U.S. administration official told Reuters news agency, \"these were difficult talks ... obviously we were far apart (at the start).\" The official, who declined to be identified due to the sensitivity of the subject, said a \"significant difference\" at the meeting was Iran\'s insistence that its right to enrich be recognised. \"Obviously (that) was not something we were prepared to do,\" the official said. \"We never expected to get that agreement (on 20 percent) here in Baghdad,\" the official said. \"There is agreement to address all aspects of 20 percent as we put it on the table.\" The official said the six powers were going to try to advance the talks \"as fast as we can\". But it was too early to talk about technical level or expert meetings because the political issues still needed to be clarified. The official said sanctions coming into effect in coming weeks would increase leverage on Iran in the negotiations. \"Maximum pressure is not yet being felt by Iran,\" the official said, adding there were many other potential sanctions that remained to be employed. Tehran wants any nuclear deal to spare it from an EU embargo on its oil exports to be phased in fully by July 1. It also wants an end to trade and diplomatic sanctions imposed since 2006.