BRUSSELS - An offer of negotiations from Iran is "basically satisfactory" and talks with global powers on Tehran's nuclear program could start soon, Swedish Foreign Minister Carl Bildt said on Monday.Facing sanctions that could cripple its oil exports, Iran said this month it wanted to resume the talks, frozen since January last year. But six big powers, represented by EU foreign policy chief Catherine Ashton, have yet to respond to the offer."We had a letter from the Iranians which was basically satisfactory," Bildt told reporters in Brussels before a meeting of European Union foreign ministers. "Now it's a question of the timing of those particular talks ... I don't know, but I don't think it's going to take too long."A spokeswoman for Ashton said on Saturday that consultations between European governments and China, Russia and the United States were still going on to decide whether to engage Iran's approach.The EU and United States have said concerns over Iran's atomic activity have increased since a new report by the International Atomic Energy Agency last week that said Tehran has sharply stepped up its controversial uranium enrichment drive.Iran says it needs nuclear energy to meet its electricity needs but global powers fear it aims to build atomic weapons.Before relaunching negotiations, global powers want assurances that Tehran is willing to directly address concerns about its nuclear campaign, something it has refused in previous, sporadic rounds of talks.