Iran nuclear talks in Switzerland
Officials from the P5 1 and the European Union wait for a meeting at the Beau Rivage Palace Hotel in Lausanne, SwitzerlandReuters

Iran and six world powers are gearing up to intensify talks to seal a nuclear deal as their self-imposed deadline looms.

Both sides scramble frantic efforts to finalise a permanent agreement as the interim deal is set to expire on Tuesday, 31 March with key sticky points remain unresolved.

The Iranian delegation led by foreign minister Mohammad Javad Zarif is expected to hold a complete session with the ministers of the P5+1 countries – the US, the UK, France, Russia, China, and Germany – in Switzerland.

"Getting to an accord is doable. Solutions have been found for numerous questions. We are still working on two or three issues... The talks are in their final phase and are very difficult," Abbas Araqchi, Tehran's key negotiator and deputy foreign minister, told reporters in Lausanne.

Though the mood of the negotiations appeared to come to a dead end over the weekend, the arrival of foreign ministers has provided a visible change in the atmosphere.

The two major sticking points are the pace in which the UN-engineered sanctions would be lifted, and limiting Iran's ability to research and development on advanced nuclear technology.

"I can't rule out that there will be further crises in these negotiations," German foreign minister Frank-Walter Steinmeier told reporters adding that there have been "some progress and some setbacks in the last hours".

Meanwhile, Iranian President Hassan Rohani has also held telephone conversation with German Chancellor Angela Merkel assuring that Tehran is easing its rigidity in the crunch talks.

"We have reached a sensitive time. Iran has shown enough flexibility in the negotiations and it is the turn of the other party to take the final steps now," said the Iranian leader.

On a separate development, Israeli Prime Minister Benjamin Netanyahu has expressed concerns that the nuclear deal with Iran appears to be worse than earlier feared.

"This agreement, as it appears, confirms all of our concerns and even more so," the fierce critic of Iran said during a cabinet meeting.