CRI听力:Iran Nuclear Deal "Possible" This Week: Kerry

US Secretary of State John Kerry says an agreement on Iran's nuclear program is possible this week if Tehran makes the "hard choices" necessary.

At the same time, Kerry is warning the United States remains ready to walk away from the negotiations.

"Over the past few days, we have in fact made genuine progress. But I want to be absolutely clear with everybody. We are not yet where we need to be on several of the most difficult issues. And the truth is, that while I completely agree with (Iranian) Foreign Minister (Mohammad Javad) Zarif that we have never been closer, at this point this negotiation could go either way."

Negotiators from Iran and world powers are meeting in Vienna to try to meet a Tuesday deadline for reaching a deal that would suspend Iran's most sensitive nuclear work in exchange for sanctions relief.

The deadline was extended from June 30th as they try to address such sticking points as how sanctions are lifted and the amount of nuclear capability Iran is allowed to keep.

European Union Foreign Policy Chief Federica Mogherini is also urging Iran to seize the chance for a deal.

"I would say that from tomorrow onwards, the next couple of days we are here to check and assess if a deal can be closed. And my message today is that if a deal can be closed it's now. It's not time, the issue is political decisions that need to be taken now."

Foreign ministers from Britain, China, France, Germany and Russia are arriving in Vienna to make a push to meet Tuesday's deadline for a final agreement to end the 12-year-old dispute.

Some diplomats have said the talks could slip to Thursday, the date by which US President Barack Obama's administration must submit a deal to Congress in order to get an expedited, 30-day review.

Republicans in the US Congress have been accusing the Obama administration of making too many concessions at the talks.