Iran's foreign minister and the European Union's foreign policy chief said a nuclear deal between Iran and six powers sealed on Tuesday heralded a new chapter of hope and was a historic moment.

"I believe this is a historic moment," Iranian Foreign Minister Mohammad Javad Zarif told a joint news conference.

"We are reaching an agreement that is not perfect for anybody but it is what we could accomplish and it is an important achievement for all of us," he said.

The deal caps more than a decade of on-off negotiations with an agreement that could potentially transform the Middle East.

Under the agreement, sanctions imposed by the United States, European Union and United Nations would be lifted in return for Iran agreeing long-term curbs on a nuclear programme that the West has suspected was aimed at creating an atomic bomb.

"Today could have been the end of hope on this issue. But now we are starting a new chapter of hope. Let's build on that," Zarif said.

The European Union's foreign policy chief Federica Mogherini said the deal sealed in Vienna after lengthy negotiations was about more than just the nuclear matter.

"It is a decision that can open the way to a new chapter in international relations and show that diplomacy, coordination, cooperation can overcome decades of tensions and confrontations," she said.

"I think this is a sign of hope for the entire world." - Reuters