Deputy Foreign Minister Abbas Araghchi said the Iranian plan's formal name was "An End to the Unnecessary Crisis and a Beginning for Fresh Horizons." He described it as having many new ideas but added negotiators had agreed to keep the details confidential during the morning bargaining session.
"We think that the proposal we have made has the capacity to make a breakthrough," he told reporters.
Alluding to the international pressure over Iran's nuclear program that has driven the country into near-pariah status, he said: "We no longer want to walk in the dark and uncertainty and have doubts about the future."
Iran's version of a grand bargain is for painful international sanctions to be lifted in exchange for possible concessions it had been previously unwilling to consider such as increased monitoring and scaling back on uranium enrichment - a potential path to nuclear arms and the centerpiece of the impasse with the West.
European Union official Michael Mann said Iran's PowerPoint presentation, presented by Foreign Minister Javad Zarif, lasted about one hour.
The session resumed in mid-afternoon and a U.S. State Department official said the five powers were looking at further details of the Iranian presentation. The official demanded anonymity because she was not authorize to divulge details of the closed meeting.
Iran's uranium enrichment program is at the core of the six world powers' concerns. Iran now has more than 10,000 centrifuges churning out enriched uranium, which can be used either to power reactors or as the fissile core of a nuclear bomb. Iran has long insisted it does not want nuclear arms - a claim the U.S. and its allies have been skeptical about - but has resisted international attempts to verify its aims.
Tehran is now under international sanctions that are biting deeply into its troubled economy. Since the election of reformist Iranian President Hassan Rouhani in June, Iranian officials have said they are ready to compromise.
The U.S, Russia, China, Britain, France and Germany are eager to test whether those words will translate into real progress such as increased international monitoring and scaling back uranium enrichment.
"We have seen some positive mood music coming out of Tehran," Mann said. "But of course the most important thing is that they actually follow it up with concrete proposals that address our concerns."
The first session of the two-day talks - the first since Rouhani's election - lasted about 2 ½ hours, ending shortly after noon. Back pains suffered by Zarif, Iran's chief negotiator, threatened to complicate the process.
Mann said the pains did not stop Zarif from having a "cordial" dinner Monday evening with Catherine Ashton, the top EU diplomat convening the talks. But Araghchi said Zarif was "suffering a lot," although he intended to stay in Geneva until the talks ended.
Iran's state TV, which closely reflects government views, said Tehran offered to discuss uranium enrichment levels. The report also said Iran proposed adopting the additional protocols of the U.N.'s nuclear treaty - effectively opening its nuclear facilities to wider inspection and monitoring - if the West recognizes Iran's right to enrich uranium.
Of the tons of enriched uranium in Iran's stockpile, most is enriched to under 5 percent - a level that need weeks of further enrichment to turn into weapons-level uranium. But it also has nearly 200 kilograms (440 pounds) of 20 percent-enriched uranium, a form that can be quickly upgraded for weapons use, according to the U.N's atomic agency, which keeps tabs on Iran's nuclear activities. That is close to - but still below - what is needed for one nuclear weapon.
No final deal is expected at the two-day session, but it potentially could be the launching pad for a deal that has proven elusive since negotiations began in 2003.
One immediate change from previous talks was the choice of language. Mann told reporters they were being held in English, unlike previous rounds under Mahmoud Ahmadinejad, Rouhani's hard-line predecessor, where Farsi translation was provided.
A former senior U.N. official who has acted as an intermediary between U.S. and Iranian officials said the six powers want significant cuts in the number of Iranian centrifuges now enriching uranium.
They also demand that Iran ship out to another country not only the 20 percent uranium it now has but also most of the tons of low-enriched uranium it has produced. And they want caps on the amount of enriched uranium that Iran could keep at any time. The official spoke on condition of anonymity because he was not authorized to comment on the talks.
Iran says it needs this material to power a future reactor network. Iranian state television has quoted Araghchi as saying that Tehran was ready to discuss its enrichment program but would never ship enriched materials abroad.
While seeking to reduce enrichment at Iran's sprawling underground facility at Natanz, the six powers also want Iran to completely close the heavily fortified enrichment plant at Fordo, south of Tehran.
Demands to reduce enrichment instead of stopping it implicitly recognize Iran's right to enrich uranium for peaceful purposes. That already is a victory for Tehran, considering talks began 10 years ago with the international community calling on the Islamic Republic to mothball its enrichment program.