The UN atomic agency's board will be looking for a way out of its impasse with Iran after two fruitless visits probing Tehran's suspected nuclear weapons drive, in a meeting starting Monday.

In a report sent to International Atomic Energy Agency member states on February 24, watchdog chief Yukiya Amano said that after the two trips, on January 29-31 and February 20-21, "major differences" with Tehran remained.

The Islamic republic denied access to the Parchin military site near Tehran where a major IAEA report in November said suspicious high-explosives tests consistent with developing nuclear warheads were carried out, Amano said.

A senior official familiar with the investigation said that the IAEA team was only able to speak to "middle men" and that the Iranians wanted to "constrain the process, and put us in a harness."

Iranian officials repeated their assertion during the trips that the November report, which has prompted tighter Western sanctions and raised speculation of Israeli air strikes, was based on forgeries, the agency said.

What response the 35 nations currently on the board of governors make this week -- the meeting is open-ended and could last until Friday -- remains to be seen, however.

"Since the November report, the IAEA has not obtained enough significant new information ... to justify additional pressure on Iran by governors," said Mark Hibbs from the Carnegie Endowment for International Peace.

It is also unclear whether Russia and China -- traditionally more lenient on Iran than their Western UN Security Council partners -- will support any resolution passed by the board condemning Iran.

In any case, beyond injecting what a second senior Western diplomat called "a deeper sense of urgency," it is unclear how useful such a resolution -- one in a long list -- would be in overcoming the deadlock.

Instead, what Amano needs is guidance on how to proceed, diplomats said,

The main hope of progress is talks "on another track" away from the IAEA, the diplomat said, namely a possible resumption of talks between Iran and the P5+1 powers -- the United States, China, Russia, Britain, France and Germany.

US President Barack Obama on Sunday said there had been "too much loose talk of war," repeating his desire for a diplomatic solution to the crisis but again warning Iran he would "not hesitate to use force when it is necessary."

North Korea, meanwhile, alongside a review of progress in improving nuclear safety close to a year since Japan's Fukushima disaster, will also be a talking point for the IAEA board.

On Wednesday, Washington announced that Pyongyang was ready to suspend its uranium enrichment programme along with nuclear and long-range missile tests, with IAEA inspectors to monitor the deal.

Another issue is Syria, which the IAEA board reported to the UN Security Council last year over a site allegedly bombed by Israel in 2007 that the agency believed was "very likely" a covert nuclear reactor.

But with Syria currently in the throes of major unrest that has left thousands dead in recent months, Damascus has told the IAEA that it is unable to hold talks on the matter at the present time, diplomats said.