Secretary of State John Kerry said Friday that the US hoped to seal a nuclear deal with Iran within the coming weeks, ahead of new talks with his Iranian counterpart.

"It remains our fervent hope that Iran and the P5+1 can in the next weeks come to an agreement that would benefit the world," Kerry said, addressing a meeting at the UN on the Comprehensive Nuclear Test Ban Treaty (CTBT).

He was speaking before he was due to later hold a second day of trilateral talks with Iranian Foreign Minister Mohammad Javad Zarif and the EU's chief negotiator Catherine Ashton in New York.

Earlier, French Foreign Minister Laurent Fabius said there had been "no progress" in the tough negotiations to rein in Iran's suspect nuclear program.

But Kerry said the talks had already borne fruit.

"The interim agreement that we struck with Iran, the P5+1, has made the world safer because a nuclear stockpile that was at 20 percent has been reduced," Kerry said.

The United States has yet to ratify the CTBT treaty, but Kerry said the administration of President Barack Obama was committed to seeing it ratified and entering into force.

Iran nuclear talks faltering amid 'no progress'
New York (AFP) Sept 26, 2014 - Top US diplomat John Kerry was to meet his Iranian counterpart Friday for a second time in two days, amid reports that tough talks on reining in Tehran's nuclear program have deadlocked.

"At this time as I speak, there is no significant progress," French Foreign Minister Laurent Fabius said of the latest discussions.

Negotiators from the so-called P5+1 group -- Britain, China, France, Russia, the United States plus Germany -- began a new round of talks here last Friday only two months before a November 24 deadline to reach a deal.

Seeking to make progress, the talks moved to a higher level Thursday when Kerry huddled late Thursday in a New York hotel with Iranian Foreign Minister Mohammad Javad Zarif and the EU's chief negotiator Catherine Ashton.

But the trilateral discussion broke up with little news filtering out and US officials did not respond to AFP inquiries about reports of a new offer on the table.

Friday's "meeting will be a continuation of the discussions the three delegations held today on Iran's nuclear program," was all a State Department official said in a terse statement.

"We will be quickly meeting again. We regret that there has been no progress," Fabius told reporters Friday on the sidelines of the UN General Assembly, adding that a ministerial level P5+1 meeting had been cancelled.

At the heart of the issue is a fundamental clash between the West's desire to dismantle Iran's capability to produce a nuclear bomb, and the Islamic republic's insistence that it should retain the capacity to enrich uranium for a civilian energy program.

The West wants Iran to dismantle virtually all but a few thousand of its 19,000 centrifuges which can be used to develop weapons-grade uranium.

But Iran bristles at destroying machines in which it has invested billions of dollars, and wants to retain many more of the centrifuges.

- Significant gaps -

Russian Foreign Minister Sergei Lavrov said Friday he remained "cautiously optimistic."

"We still have time," he told reporters at UN headquarters in New York as the clock ticks down to November.

"We will do our utmost to make sure that remaining small, but extremely important, issues be resolved in a way that is acceptable to all," Lavrov said.

A western diplomat said a lot of technical work had been done during the week on some of the core issues including enrichment and sanctions.

"When I say there are significant gaps, it means that we are still expecting significant moves from the Iranian side," the diplomat said, adding the level of "mistrust is pretty high."

Complicating the talks are domestic politics.

Under a 2013 interim deal, Iran agreed to freeze parts of its nuclear program and allow daily inspections of some nuclear sites in return for a partial release of billions of dollars from blocked oil revenues.

But US lawmakers are already drawing up more sanctions against Washington's arch-foe, while Iranian leaders are under pressure to achieve an end to the crippling economic measures without conceding too much.

The final deal would aim to ease fears that despite its denials Iran is seeking to develop an atomic bomb, by expanding the time needed for Tehran to make such a weapon and allowing for a tough monitoring regime by the UN nuclear watchdog, the IAEA.

"The objective is really to have Iran reduce significantly its enrichment capacity," the western diplomat said.

"In return the six are ready to lift sanctions step by step, starting with the EU sanctions and the US unilateral sanctions. That's a huge reward for the Iranians."

Analysts fear, however, that even if a deal is reached, Iran could try to secretly continue to develop its nuclear capabilities.

"The intelligence community judges it more likely that Tehran would choose a clandestine effort, sometimes called 'sneakout,' not using facilities that it had declared to the IAEA," wrote Greg Thielmann from the Arms Control Association.

"This would theoretically allow Iran to minimize the international community's warning time and ability to take effective blocking action."