Kerry urges Iran to make 'hard choices', says US ready to walk

Speaking during a break from one of his four meetings with Iranian Foreign Minister Mohammad Javad Zarif on July 5, Kerry said they had made "genuine progress" in talks over the last few days but "several of the most difficult issues" remain.

"If hard choices get made in the next couple of days, made quickly, we could get an agreement this week, but if they are not made we will not," he said in Vienna, where talks between Iran, the United States and five other powers are being held.

Foreign ministers from Britain, China, France, Germany and Russia began arriving on July 5 evening as the major powers make a push to meet July 7's deadline for a final agreement to end the 12-year-old dispute.

Kerry said negotiators were still aiming for that deadline, but other diplomats have said the talks could slip to July 9, the date by which the Obama administration must submit a deal to Congress in order to get an expedited, 30-day review.

The agreement under discussion would require Iran to curb its most sensitive nuclear work for a decade or more in exchange for relief from sanctions that have slashed its oil exports and crippled its economy.

While they have made some progress on the type of bilateral sanctions relief that Iran may receive, the two sides remain divided on such issues as lifting United Nations sanctions and on its research and development of advanced centrifuges.

Diplomats close to the negotiations said they had tentative agreement on a mechanism for suspending US and European Union sanctions on Iran.

But the six powers had yet to agree with Iran on a United Nations Security Council resolution that would lift UN sanctions and establish a means of re-imposing them in case of Iranian non-compliance with a future agreement.

In addition to sanctions, other sticking points include future monitoring mechanisms and a stalled UN probe of the possible military dimensions of past Iranian nuclear research.

Senior officials from the International Atomic Energy Agency, the UN nuclear watchdog, plan to visit Iran this week.