Iran's negotiators are expected to offer restrictions on its nuclear programme in return for at least a partial lifting of sanctions, at a new round of talks starting in Geneva on Tuesday, diplomats said.

The complexity of the proposals means a completed deal is unlikely at the end of two days of negotiations, as there will remain significant gaps between the Iranian and western negotiating positions, but diplomats pointed to a new level of engagement not seen for several years.

The Iranian foreign minister and lead negotiator, Mohammad Javad Zarif, posted a message on his Facebook account saying the Geneva talks were "the start of a difficult and relatively time-consuming way forward".

He said: "I am hopeful that by Wednesday we can reach agreement on a road map to find a path towards resolution. But even with the goodwill of the other side, to reach agreement on details and start implementation will likely require another meeting at ministerial level."

The Iranian road map for the talks was described in vague terms on Friday by Zarif's deputy, Abbas Araqchi, who said Tehran would negotiate "the form, amount, and various levels of [uranium] enrichment" but would not agree to shipping enriched uranium out of the country.

Elements of the plan were floated in more detail during a visit to the UN in New York last month by Zarif and the newly-elected president, Hassan Rouhani, the Guardian has learned.

Iranian officials said Tehran would be prepared to limit its enrichment programme to two facilities, possibility both at Natanz, suggesting a readiness to suspend enrichment at a sensitive underground site at Fordow.

Iran is also prepared to suspend production of 20%-enriched uranium – another major concern for the international community as it is relatively straightforward to convert it into 90% weapons grade material.

Tehran will not agree to surrendering its existing stockpile of the 20% medium-enriched uranium, currently about 190kg, but compromises are possible that would make it less of a proliferation concern. It could be kept under international monitoring in a remote corner of the country, or it could be turned into reactor fuel, a form which is harder to enrich further.

Iran is also prepared to negotiate on the number of centrifuges it uses to make 3.5% enriched uranium, suitable for fuel for nuclear power stations, and on how much each centrifuge makes. Iranian officials have pointed out that, although new model centrifuges, called IR-2M, have been installed, they are not yet being fed with uranium gas for enrichment, and they pointed to that as an example of how the enrichment programme could be calibrated by international agreement.

Furthermore, the Iranians suggested that work on a heavy-water reactor at Arak, which would produce plutonium when commissioned, had been delayed since Rouhani's election and could be put off further if an interim deal was reached.

Tehran has also revived a longstanding proposal of forming a consortium with other countries to enrich uranium in Iran, as a means of reassuring the international community it would not be diverted for weapons purposes. In return, Iran would expect significant sanctions relief, and recognition that it had the right in principle to enrich uranium.

If the elements floated in New York are set out in Zarif's road map, it would represent the most substantive Iranian offer in a decade. However there would still be significant points of difference with the six nations represented at the Geneva talks: the US, UK, France, Germany, Russia and China, chaired by the EU foreign policy chief, Catherine Ashton.

The group has demanded the underground facility at Fordow be closed down entirely as part of a confidence-building deal. Iran is likely to accept suspension of enrichment there but not permanent closure.

Similarly, western powers had called for the transfer of the total stock of 20% enriched uranium out of the country, and it is unclear whether its conversion to reactor fuel or warehousing inside Iran would satisfy Washington and its allies.

The US is also reluctant to declare Iran's right to enrich uranium openly as early in the process as Tehran would like, fearing it would set a precedent for many other nations to start building centrifuge plants of their own, multiplying the risk of global nuclear proliferation.

Lastly, there is a gaping divide between the scale of sanctions relief Iran is demanding, involving the lifting of oil and financial embargoes, and the much more limited concessions offered by the west, covering aircraft parts, gold and petrochemical exports.

Iran observers, however, are hopeful that creative diplomacy at Geneva can help close some of those gaps.

"The Iranians are confident. They have a game plan and they are looking to execute that plan," said Jim Walsh, an expert on the Iranian nuclear programme at the Massachusetts Institute of Technology.

"They are aware of the political sensitivities in the US. They get it, but they have sensitivities of their own and their clock is ticking for them to produce some results. They are ready for a small deal. Not a grand bargain, but a small deal.

Our concern on the American side is do we have our act together. I still don't have the answer to that question."

The Obama administration's room for negotiation is limited by what Congress would accept which in turn is influenced partly by Israel's position. Israel has warned of the dangers of the P5+1 talks in Geneva producing a "bad agreement" along the lines of those signed with North Korea, which did not prevent Pyongyang developing nuclear weapons.

As part of the diplomatic and media offensive launched by the Israeli government ahead of this week's talks in Geneva, intelligence and strategic affairs minister Yuval Steinitz told foreign journalists: "We have to learn from history, and the mistakes of history, and be very clear that not every agreement is a genuine political achievement." He stressed that Israel had not "closed the door to a diplomatic solution" to the Iranian nuclear issue, "on condition that it is a satisfactory solution".

"We do hope this process will succeed, that there will be a satisfactory diplomatic solution. We hope that we will not repeat the terrible mistakes of North Korea. This is our hope and we should all do our best to ensure that Geneva 2013 will not become Munich 1938," he said, referring to the pre-second world war agreement regarded as an act of appeasement by European powers to Nazi Germany.

In contrast to the agreements made with North Korea, the minister cited Libya as a successful model. "This agreement was about dismantling nuclear capacity, destroying centrifuges and giving up enrichment facilities," he said.

In contrast to previous statements made by Israeli leaders, Steinitz played down the necessity of a credible military threat against Iran, instead warning against the premature lifting of economic sanctions. "The economic pressure [on Iran] is very significant. The greater the pressure, the greater the chance of diplomacy to succeed. The Iranians are coming to the table because of severe economic pressure."

Sanctions must not be eased before a final satisfactory solution, he added. "A credible military threat would increase the chances of success but maybe you can succeed without that."

The "rational and logical" outcome of the Geneva talks was to allow Iran to produce nuclear power for civilian use, using fuel bought from abroad, as Canada, South Africa, Sweden and other countries do, he said. "This is a win-win situation – Iran gets what it says it wants, and the rest of the world is confident they are not producing nuclear weapons."