'Real gaps' on key issues in Iran n-talks: Kerry

Participating sides will continue to work to bridge the remaining "real gaps" on some key issues in Iranian nuclear talks as the July 20 deadline approaches, US Secretary of State John Kerry said here Tuesday.

"There has been tangible progress on key issues... however, there are also very real gaps on other key issues," Kerry told reporters.

"It is clear we have more work to do," added Kerry, saying that he was returning to Washington Tuesday to consult with US President Barack Obama and with Congress leaders over the coming days the prospects for a comprehensive agreement as well as the path forward if sides could achieve the agreement by the deadline July 20 based on the progress made.

He also added that the sides would continue work on the issue with the belief that "there is a way forward", and that "the July 20 deadline is still on the table", he noted, according to Xinhua.

The remarks came after days of intensive and a variety of bilateral and trilateral meetings between the US, the European Union (EU) and Iran's top diplomats in Vienna.

Th six major world powers or the P5+1 group comprising the US, France, Britain, Russia China plus Germany, have been seeking a deal to settle the decades-old dispute over Iran's nuclear programme.

A six-month interim deal, which took effect Jan 20 and would expire five days later, was designed to buy time for negotiations for a final agreement. Under the interim deal, Iran agreed to suspend some sensitive nuclear activities in exchange for limited sanctions relief.

When asked about Iran's supreme leader's remarks about Tehran's nuclear ambition, Kerry said number of centrifuges Iran claimed were too many.

Iran's supreme leader Ayatollah Ali Khamenei said Tuesday that Iran needed 190,000 separative work units (SWUs) for uranium enrichment (around the 190,000 to 237,500 output capacity of IR-1 Iranian centrifuges), much higher than the West currently wants to allow under a comprehensive agreement.