Obama says more Iran sanctions coming if talks drag

US President Barack Obama said there would be more sanctions imposed on Iran if there is no breakthrough in nuclear talks with global powers in the coming months, responding to Israeli accusations that Tehran has been given a "freebie."

At a news conference in Cartagena, Colombia, where he was attending the Summit of the Americas, Obama said negotiations between Iran and six world powers that resumed on Saturday would not stretch on indefinitely and would require Iran to act.

"We're going to keep on seeing if we make progress. Now, the clocking is ticking and I've been very clear to Iran and to our negotiating partners that we're not going to have these talks just drag out in a stalling process," Obama said. "But so far at least we haven't given away anything."

Negotiators from Iran and six world powers met on Saturday for the first time in more than a year to discuss concerns about Tehran's nuclear program, which Iran says is for energy and others fear is meant to build an atomic bomb.

The group, which included the United States and the other four permanent UN Security Council members Britain, France, China and Russia, plus Germany, agreed with Iran to reconvene in Baghdad on May 23.

Israeli Prime Minister Benjamin Netanyahu voiced irritation that the next talks were in more than a month's time, saying it was critical that Tehran stop enrichment right away.

"My initial impression is that Iran has been given a freebie. It's got five weeks to continue enrichment without any limitation, any inhibition," he said earlier on Sunday.

Over the past year, Israeli and US warnings of military strikes if Iran does not stop working on some aspects of nuclear technology have stoked fear of war, and raised oil prices, in an unsettled Middle East.

Obama, who is up for re-election in November, is unlikely to want to start a military dispute with Iran, especially as he works to withdraw US forces from Afghanistan and in the wake of an unpopular war in Iraq.

At the Colombia news conference, Obama said there was still time for talks to ease tensions surrounding Iran.

"We still have a window in which to resolve this conflict diplomatically. That window is closing and Iran needs to take advantage of it," he said.