US Energy Secretary Ernest Moniz was heading to Geneva Saturday to join talks with Iranian officials as efforts for an historic nuclear deal stepped up a gear.

US Energy Secretary Ernest Moniz was heading to Geneva Saturday to join talks with Iranian officials as efforts for an historic nuclear deal stepped up a gear.

It was the first time that Moniz, who is himself a nuclear physicist, had joined the negotiations, although US energy officials have been involved in the intensive technical talks under way ahead of new meetings between the countries' top diplomats on Sunday and Monday.

"At the request of Secretary of State John Kerry, Secretary of Energy Ernest Moniz will travel to Geneva on Saturday to join Secretary Kerry in continued negotiations with Iran over its nuclear program," an energy department spokesman said.

"Department of Energy officials have consistently been involved in these in-depth technical discussions as part of the US negotiating team and Secretary Moniz will be joining the team in Geneva to continue these ongoing detailed technical deliberations."

A second day of technical talks was to be held on Saturday and the director of the Iranian Atomic Energy Organization Ali Akbar Salehi flew to Geneva to meet Moniz as part those discussions, Iranian officials said.

"Salehi will hold talks on the technical aspects of the negotiations with the P5+1 group with US Energy Secretary Ernest Moniz," IAEO spokesman Behrouz Kamalvandi said.

Senior negotiators from the six powers -- Britain, China, France, Germany and Russia as well as the United States -- are also to meet in Geneva on Sunday in a bid to drive the talks forward, the European Union said.

Zarif and Kerry have held repeated meetings in recent weeks as the clock ticks down to March 31 for the political framework of a comprehensive deal on Iran’s nuclear program.