ISTANBUL // As world powers and Iran agreed to launch additional talks about Tehran's nuclear programme, western diplomats and politicians warned that concrete Iranian concessions would be needed to keep the process alive.
"The proof of the pudding is in the eating," one diplomat said late on Saturday after a day of talks in Istanbul between the five nations with veto power in the United Nations Security Council - the United States, Russia, China, France and the United Kingdom - as well as Germany and an Iranian delegation.
"The ball is clearly in the Iranians' court," he said.
Israel's prime minister said yesterday that Iran got a "freebie" at the talks. Benjamin Netanyahu said the arrangement gave Iran five weeks to continue uranium enrichment - a process that can be used both in the production of nuclear energy or nuclear weapons - without any restrictions. He said Iran should be forced to stop this immediately.
Catherine Ashton, the EU foreign policy chief and leader of the six-nation delegation, told reporters after Saturday's meeting the two sides would meet in the Iraqi capital on May 23
Saturday's meeting did not address concrete steps to ease tensions over the nuclear programme, which the West suspects could have military purposes.
Ms Ashton said both sides agreed the non-proliferation treaty, designed to prevent the spread of nuclear weapons, should form the basis for further discussions, but she also acknowledged "Iran's right to the peaceful use of nuclear energy".
She said further talks would be "guided by a step-by-step approach and reciprocity", a reference to the Iranian position that concessions on the nuclear programme should be answered by an easing of western sanctions against Tehran.
"We expect that subsequent meetings will lead to concrete steps towards a comprehensive negotiated solution, which restores international confidence in the exclusively peaceful nature of the Iranian programme," she said.
The White House applauded the "positive attitude" of both sides in the Istanbul talks, but repeated its demand for Tehran to take "concrete steps".
The British foreign secretary, William Hague, said further talks should strengthen confidence that "Iran will implement its international obligations and does not intend to build a nuclear weapon".
The French foreign minister, Alain Juppe, also urged Iran "to make urgent and concrete gestures to establish confidence".
Officials from both sides are to meet before the conference in the Iraqi capital to look for possible compromises. Western diplomats said consultations between the countries negotiating with Iran would be necessary as well.
Saeed Jalili, the Iranian top negotiator, called the meeting in Istanbul "successful". But he hinted at unsolved problems.
Standing under a banner put up by Iranian officials that read "Nuclear energy for all - nuclear weapons for none", he said in Istanbul late on Saturday that a "strategy of threat doesn't work", in an apparent reference to Israel's threat to attack Iran's nuclear facilities.
Mr Jalili said a religious ruling issued by Iran's supreme leader, Ayatollah Ali Khamenei, stating that weapons of mass destruction violate Islamic law was received positively by western negotiators.
But western diplomats said the ayatollah's statement stood in contrast to Iranian actions in the nuclear programme. The US and European countries are especially concerned about Iran's programme of uranium enrichment and a lack of transparency in its dealings with inspectors of the International Atomic Energy Agency.
The Istanbul meeting was the first attempt to solve the row surrounding the Iranian nuclear programme since a previous round of talks, also in Istanbul, ended without agreement in January last year.