A five-point plan outlined by Russian Foreign Minister Sergei Lavrov in 2011 proposed a gradual easing of economic sanctions against Tehran in exchange for increased collaboration with the International Atomic Energy Agency (IAEA), the Vienna-based global nuclear watchdog.

The European Union has pitched a separate three-stage plan for Tehran's nuclear program, Iran’s Foreign Minister Ali Akbar Salehi said in an interview with RIA Novosti earlier this month, but refused to elaborate on the details.

Michael Mann, spokesman for EU foreign policy chief Catherine Ashton, said on Monday the six-nation group of negotiators has prepared a “good and updated offer for the talks, which we believe is balanced and a fair basis for constructive talks.”

“The offer addresses international concerns... on the nature of the Iranian nuclear program, but is also responsive to Iranian ideas,” Mann said, without disclosing the details of the new offer. Earlier this month, Ashton called on Iran to show flexibility in negotiations in order to achieve progress.

According to a US delegation source, Washington will put forward proposals to Iran which will help find diplomatic ways to resolve the deadlock over the controversial nuclear program.

Tehran is expected to hold bilateral meetings with the representatives of the group of negotiators after the plenary session starts, a source in the Iranian delegation told RIA Novosti on Tuesday.

Ahead of the talks, Russian Deputy Foreign Minister Sergei Ryabkov said that success at the negotiations depends on “political will” from both sides and a breakthrough could be expected only if Tehran proves its nuclear program is peaceful.

Russia has repeatedly expressed concern over the slow pace of the nuclear talks with Iran, and stressed the need for the new meeting to be held as soon as possible.

Iran is under four sets of economic sanctions based on UN resolutions, as well as a number of sanctions imposed unilaterally by some Western countries.

Iran and the Group of Six countries (Britain, China, France, Russia, the United States and Germany) have held three rounds of talks over the Iranian nuclear issue last year, following a one-year break in the negotiations. Those talks, however, remained deadlocked.

The Almaty talks come just days after Iran announced it was putting into service at its Natanz facility new high-performance gas centrifuges for enriching uranium - an essential precursor to making high-grade nuclear fuel or the raw material for a nuclear weapon.

The western allies and Israel have accused Iran of using its nuclear program to develop atomic weapons capability, a claim Iran has consistently denied. Tehran claims it needs atomic technology for producing electricity, although it has some of the world's largest reserves of oil and gas.