(CNN) -- Israel on Sunday slammed a decision by key world powers to place no new restrictions on Iran before the next meeting about its nuclear program in late May.

"My initial impression is that Iran has been given a freebie," Prime Minister Benjamin Netanyahu said. "It has got five weeks to continue enrichment without any limitation, any inhibition."

On Saturday, negotiators said "constructive and useful" talks had taken place in Istanbul.

"We have agreed that the Non-Proliferation Treaty forms a key basis for what must be serious engagement to ensure all the obligations under the treaty are met by Iran while fully respecting Iran´s right to the peaceful use of nuclear energy," EU foreign policy chief Catherine Ashton said following the meeting with Iran´s top negotiator, Saeed Jalili.

The five permanent members of the United Nations Security Council, the United States, France, Russia, China, and Britain -- and Germany, referred to as the P5+1, scheduled the next set of talks May 23 in Baghdad.

Iran on state-run news agency IRNA pointed to a statement from Russia describing the talks as constructive and "based on mutual respect."

"Iran´s top nuclear negotiator, Saeed Jalili, said after the Istanbul meeting that talking about suspending or halting uranium enrichment was an old issue now out-of-date," IRNA reported.

But Netanyahu said Iran should "take immediate steps to stop all enrichment, take out all enrichment material and dismantle the nuclear facility in Qom," and said the Islamic republic "must not have the opportunity to develop atomic bombs."

Iran insists its nuclear program is for energy purposes only. U.N. and Western leaders suspect it of having military aims, including a possible nuclear weapon.

Last month, the International Atomic Energy Agency, the U.N. nuclear watchdog, noted what it called a sharp and troubling increase in Iran´s uranium enrichment capabilities. (© 2012 Cable News Network 04/16/12)