Iran has bought itself extra time during a first round of key talks with world powers over its disputed nuclear programme, Israeli Prime Minister Benjamin Netanyahu said on Sunday.

"My initial impression is that Iran has been given a ´freebie´," Netanyahu said during talks with visiting US Senator Joe Lieberman, the premier´s office reported.

"It has got five weeks to continue enrichment without any limitation, any inhibition. I think Iran should take immediate steps to stop all enrichment, take out all enrichment material and dismantle the nuclear facility in Qom," he said.

"I believe that the world´s greatest practitioner of terrorism must not have the opportunity to develop atomic bombs," he said.

At Saturday´s talks in Istanbul, during which Iranian officials sat down with the so-called P5+1 grouping of diplomats from the United States, Russia, China, Britain, France and Germany, the sides agreed to hold a more in-depth meeting in Baghdad on May 23.

Officials described the talks as positive but stressed that a great deal was expected of Iran at the next meeting.

The UN Security Council has slapped four rounds of sanctions on Tehran over suspicions harboured by Israel and much of the West that Iran is seeking a militarised nuclear capability -- a charge which Tehran denies.

Of special concern is Iran´s formerly secret Fordo site located deep inside a mountain bunker near the holy city of Qom that is enriching to 20 percent purity but which experts say could be reconfigured to produce 90 percent weapons-grade material.

Israel, which sees a nuclear Iran as an existential threat, has not ruled out a preemptive strike on Iranian nuclear facilities. (Copyright © 2012 Agence France Presse. 04/16/12)