Negotiators from Iran and six world powers hunkered down Thursday to a second day of talks aimed towards what could be a historic deal on Tehran’s nuclear program.

Negotiators from Iran and six world powers hunkered down Thursday to a second day of talks aimed towards what could be a historic deal on Tehran's nuclear program.

A spokesman for Catherine Ashton, EU foreign policy chief and the powers' lead negotiator, said only that the first day's discussions were "intensive and useful" and that the "hard work" would continue Thursday.

A US State Department official said that "coordination and experts meetings will resume and continue throughout the day" at a hotel in the Austrian capital.
After three earlier rounds, this time Iran and the five permanent members of the UN Security Council plus Germany aim to start drafting the actual text of what could be a landmark agreement.

The parties want to get a deal by July 20, when a November interim deal under which Iran froze certain activities in return for some sanctions relief expires.

The United States, Russia, China, Britain, France and Germany want Iran to radically scale back its nuclear activities.   

In return the Islamic republic, which firmly denies wanting atomic weapons, wants the lifting of all UN and Western sanctions, which have caused its economy major problems.

"Quite frankly, this is very, very, difficult. I would caution people that just because we will be drafting it certainly doesn't mean an agreement is imminent or that we are certain to eventually get to a resolution of these issues," a senior US official said Tuesday.

The talks are tentatively scheduled to last until Friday, with Iranian Foreign Minister Mohammad Javad Zarif telling national media on Tuesday that he expected three more rounds before July 20.