Kerry: Nuclear deal with Iran 'closer than ever'

Western powers and Iran are "closer than ever" to a comprehensive deal on the Iran's nuclear programme, US Secretary of State John Kerry said on Monday.

Kerry's remarks came on the first day of a UN conference to review the implementation of the global anti-nuclear weapons treaty.

Earlier this month, Iran and the P5+1 countries - US, Russia, UK, France, China plus Germany - reached a framework deal that envisages Tehran curbing its nuclear activity in exchange for sanctions relief.

The parties have until 30 June to reach a final agreement.

"I want you to know the hard work is far from over and some key issues remain unresolved. But we are, in fact, closer than ever to the good comprehensive deal that we have been seeking," Kerry said.

"And if we can get there, the entire world will be safer," he added.

With regards to his country's atomic arsenal, Kerry said the US's nuclear stockpile now stood at its lowest level since the Cold War – down to 4,717 warheads as of last September.

He said the US had eliminated more than 10,000 warheads in the past 20 years.

"We have and we will continue to scale down our arsenal, and to continue to move, step by step, toward nuclear disarmament," he said.

Russia and the US possess more than 90 percent of the world’s nuclear warheads.

Earlier in the day, Iran's Foreign Minister Javad Zarif demanded countries possessing nuclear weapons "immediately cease their plans to further invest in modernising and extending the life span of their nuclear weapons and related facilities."

"The continued existence of nuclear weapons poses the greatest threat to humanity," he said at the start of the conference.

China, France, Russia, UK, and the US – the five permanent members of the UN Security Council – are officially recognised as possessing nuclear weapons by the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the world's primary nuclear disarmament pact.

Kerry and Zarif held a closed meeting on Monday on the sidelines of the conference to discuss efforts to reach a long-term nuclear deal, according to media reports.

Iran's Rouhani warns change coming for 'sanctions busters'

Meanwhile, Iranian President Hassan Rouhani warned Tuesday that middlemen who have circumvented sanctions will need to "think of another job" as the potential final nuclear deal brings changes to Iran's economy.

The remarks signalled Rouhani's intent to tackle a black market that has thrived in Iran after official trading routes were cut off.

Although sanctions plunged the economy into recession and hurt most of the population, some Iranians have amassed fortunes from smuggling foreign goods.

"Sanctions busters should now think of another job," Rouhani said.

"With the final agreement -- which if the other side has serious determination will be possible in the coming months -- production and the economic situation will be much better."

Rouhani had made a similar warning at the same time last year, saying "a small, fringe group is very angry" about sanctions being lifted under a nuclear deal "because they will suffer losses".

Since the signing of an interim agreement in November 2013 that eased the sanctions regime, foreign trade delegations have visited Iran with a view to resuming trade after a final agreement.

About two dozen American businesspeople visited Tehran last week and a large delegation from Switzerland, the first in 10 years, arrived Sunday for four days of consultations with politicians and economists.

Large foreign companies in the oil and automotive industries have also made contacts for a return to Iran if sanctions are lifted.