G8 leaders on Saturday pressured Iran to comply with demands by the international community that it come clean about its nuclear program.
The call at the annual summit of Group of Eight industrial countries came just days before a crucial meeting about Iran's nuclear program in Baghdad.
"We desire a peaceful and negotiated solution to concerns over Iran's nuclear program, and therefore remain committed to a dual-track approach," the G8 leaders said as their summit came to a close at the US presidential retreat.
The dual-track refers to the combination of heavy sanctions and serious talks.
Iran says its nuclear facilities are for peaceful use only.
The G8 expressed "grave concern" about Iran's nuclear program, which is suspected of being used to develop nuclear weapons, and called on Iran to "seize the opportunity" of the next round of meetings.
Iran is to meet with the P5 + 1 group of China, Russia, France, Britain, Germany and the US in Baghdad on Wednesday.
At the G8 summit, Obama said he was "hopeful" about the discussions, "but all of us are firmly committed to continuing with the approach of sanctions and pressure, in combination with diplomatic discussions," he said.
The chief of the UN nuclear agency, Yukiya Amano, is to visit Iran on Monday to prepare the groundwork for Wednesday's meeting. Sources near the International Atomic Energy Agency in Vienna told dpa that Amano's trip on short notice was a positive development.
Iran has also called Amano's visit a "good sign."
Sanctions on Iran have escalated from those on an ever-expanding list of Iranian officials and companies to the oil industry and banks that handle foreign payments.
The moves have taken a toll on the Iranian economy. According to a report from the Organization of the Petroleum Exporting Countries, oil production fell by 12 per cent in the first three months of this year, The New York Times reported.
Iranian officials say the boycott has had no effect.
Israel remains skeptical about the talks. Prime Minister Benjamin Netanyahu said Friday he has seen "no evidence that Iran is serious about stopping its nuclear weapons program."
"They may try to go from meeting to meeting with empty promises. They may agree to something in principle but not implement it.
They might even agree to implement something that does not materially derail their nuclear weapons program," he said.
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