Iran and six world powers are struggling to narrow their differences in a nuclear agreement.

That was the take away on Wednesday in Vienna, where top negotiators met for two days as they draft an agreement curbing Tehran's nuclear ambitions.

European Union Policy Chief Catherine Ashton is coordinating the talks for the six world powers.

(SOUNDBITE) (English) EU FOREIGN POLICY CHIEF, CATHERINE ASHTON, SAYING:

"A lot of intensive work will be required to overcome the differences which naturally still exist at this stage in the process. We will now move to the next phase in the negotiations in which we will aim to bridge the gaps in all the key areas and work on the concrete elements of a possible comprehensive agreement."

Iranian Foreign Minister Mohammad Zarif read an identical statement in Farsi.

(SOUNDBITE) (Farsi) IRAN'S FOREIGN MINISTER, MOHAMMAD ZARIF, SAYING: (READING SAME STATEMENT AS THAT OF ASHTON)

"We will now move to the next phase in