Iran urged Western powers to engage in "purposeful" negotiations Tuesday as top EU and Iranian representatives meeting in Istanbul looked for a breakthrough on restarting talks over Tehran's nuclear program. Pressure to get back to the bargaining table was rising the day after Iran's nuclear chief harshly attacked the integrity of the U.N.'s atomic energy organization and its investigation of allegations Iran is working on nuclear arms. Fereydoun Abbasi's defiant speech to the International Atomic Energy Association was sure to bolster hardline Israeli views that diplomatic efforts and economic penalties have had no effect on Iran, leaving military strikes as the only alternative. In this photo provided by Turkish Prime Minister's Press Service, Turkish Prime Minister Recep Tayyip Erdogan, left, greets Iran's chief nuclear negotiator Saeed Jalili before a meeting in Ankara, Turkey, Tuesday, Sept. Iran on Tuesday urged Western powers to engage in "purposeful" negotiations as top EU and Iranian representatives prepared to meet for talks on restarting stalled negotiations over Tehran's nuclear program. The EU's Foreign policy Chief Catherine Ashton and Jalili are meeting in Istanbul later on Tuesday. (AP Photo/Yasin Bulbul, Prime Minister's Press Service) Close Tuesday's meeting between EU foreign policy chief Catherine Ashton and Iran's chief nuclear negotiator Saeed Jalili follows a round of talks in July in which an attempt was made to restart nuclear negotiations between Tehran and six world powers that fizzled in June. "Negotiations should be purposeful; talks for talks would not be effective," Ramin Mehmanparast, spokesman for the Iranian Foreign Ministry said Tuesday. We can cross the finish line only when the other side enters the talks with real motivation and strong will to solve the issue. On Monday, Abbasi told the IAEA's 155-nation general conference that "terrorists and saboteurs" might have infiltrated the agency in an effort to detail his nation's nuclear program, in Tehran's harshest attack on the integrity of the U.N. organization. Abbasi said there were two sabotage attempts on his country's nuclear program. In Tehran, the director of a private think tank with close links to the government said an agreement between Iran and the Western powers could emerge at the talks. "An implicit, temporary and gradual deal between the two sides will be made," Amir Mousavi, director of the Center for Strategic Studies and International. Both the U.S. and other Western countries seek international and regional calm and stability.