Harsher sanctions will be imposed on Iran despite Tehran having engaged in two rounds of talks with world powers over the issue of its disputed nuclear program, with a third round scheduled for next month, Army Radio quoted a senior US official as saying in a briefing to reporters in Tel Aviv on Saturday.The official, who was said to have intimate knowledge of the negotiations with Iran which took place in Baghdad this past week, said that the US would continue to pressure Iran with sanctions until it ceased enriching uranium. The US official said that even after the third round of talks next month in Moscow, it will likely not be certain if Iran is engaging in talks to buy time to continue pursuing nuclear weapons or if it is serious in its intentions to come to an agreement with the P5+1 group of world powers, consisting of the US, UK, France, China Russia and Germany. Israel's concerns that "time is running out" on the Iranian nuclear issue are justified, according to the official. "We are doubtful it is possible to reach an agreement with Iran, but we must exhaust the diplomatic path - because the alternative, whether its a nuclear Iran or a regional war, is very serious," Army Radio quoted him as saying.According to the official, Iran will not be the recipient of good will gestures from the West just because of its willingness to take part in talks. Tehran must exhibit concrete actions if it wants to see its sanctions reduced, the official said. "The western world, including Russia and China is united against Iran and believes that sanctions are effective and must continue to be imposed," he added.After discussions in Baghdad extended late into an unscheduled second day on Thursday between envoys from Iran and the six powers, European Union foreign policy chief Catherine Ashton said it was clear both sides wanted progress and had some common ground, but significant differences remained."We will maintain intensive contacts with our Iranian counterparts to prepare a further meeting in Moscow," she told a news conference in Baghdad.The next meeting, the third in the latest round of talks that began in Istanbul last month after a diplomatic vacuum of 15 months, will be held in Moscow on June 18-19.