Representatives from Iran and the United States were poised to meet in Geneva on Monday for their first full-scale official talks in decades aimed at bridging the gaps in negotiations for a deal on Teheran's disputed nuclear program.

Neither the location nor the program of the two-day meeting has been announced. However, the main issue is expected to be finding a route toward an eventual lifting of sanctions against Iran.

Abbas Araqchi, a vice-foreign minister who will lead the Iranian delegation, said on Sunday that the tete-a-tete with US officials was essential as the negotiations are delicately poised.

The P5+1 group of permanent members of the Security Council - the United Kingdom, China, France, Russia and the United States, plus Germany - have long sought to reach a settlement over Iran's nuclear program. But with the last round of talks in Vienna in May yielding next to no progress, there has been concern that the P5+1 process was stalling.

The announcement on Saturday of the US-Iran meetings in Geneva came as a surprise, but appeared to confirm the need for secondary steps to close big gaps between Teheran's and Washington's positions.

"We have always had bilateral discussions with the United States in the margin of the P5+1 group, but since the talks have entered a serious phase, we want to have separate consultations," Araqchi said, quoted by the IRNA news agency.

"Most of the sanctions were imposed by the US, and other countries from the P5+1 group were not involved," he added, in a telling remark about how the US stance remains Iran's main concern.

A senior US administration official said on Saturday that the Geneva talks would "give us a timely opportunity to exchange views in the context of the next P5+1 round in Vienna," between June 16-20. The talks are aimed at securing a comprehensive agreement on Iran's nuclear activities, which the West suspects is aimed at developing weapons, but which Iran insists is for peaceful purposes.

After decades of hostility, Iran and the US made the first tentative steps toward rapprochement after the election of self-declared moderate Hassan Rouhani as president last June.

An interim deal struck in November led the US and its partners to release $7 billion from frozen funds in return for a slowdown in Iran's uranium enrichment.

But a long-term accord, ahead of a July 20 deadline, remains a long way off, experts say.

Cyrus Nasseri, a member of Iran's nuclear negotiating team when it was led by Rouhani between 2003 and 2005, told AFP the US role as "the main interlocutor" explained the need for direct talks, and said Washington had to drop its "stubbornly recalcitrant" outlook.

"It's all a matter of whether the US will be prepared to take the next step to accept a reasonable solution which will be win-win for both," with Iran allowed to maintain a uranium enrichment program, he said.

"The US has to bite the bullet after 10 years of wrongful accusations. It has to accept Iran will at the end of day, no matter how the settlement is made, have peaceful nuclear fuel production."

(China Daily 06/10/2014 page12)