Iran has renewed its pledge not to seek nuclear weapons during talks in Geneva with European Union countries.
Iran is threatening to restart its enrichment programme
The announcement was made by UK Foreign Secretary Jack Straw who said the discussions had been "complex".
The Europeans are to give Iran detailed proposals on implementing the Paris deal on suspending enrichment, he said.
Chief Iranian negotiator Hasan Rohani said an agreement could be reached "within a reasonably short time". But a decision would be taken in Tehran.
Europe has threatened to refer Iran to the UN Security Council - and possible sanctions - if it resumes uranium enrichment.
The US says Tehran is trying to develop nuclear weapons.
Iran insists its programme is for civilian use only.
The EU has until now employed a more conciliatory approach, offering economic and political incentives to keep enrichment activities frozen in line with the Paris deal struck in November.
Iran's announcement earlier in May that it was considering resuming uranium enrichment triggered Europe's invitation to the Geneva talks.
They took place as more than 180 states continue with discussions at the UN on strengthening the Nuclear Non-Proliferation Treaty.
Iran's nuclear programme, along with North Korea's nuclear ambitions, are widely believed to be a key obstacle in the NPT talks, although critics also point to a lack of US leadership.
Mr Straw was joined at the talks by his French and German counterparts - known as the EU3 - and the EU foreign policy chief.
After the discussions at the Iranian embassy in Geneva, Mr Straw said a fresh set of European proposals on implementing the Paris agreement would be submitted to the Iranians by the end of July or the beginning of August.
"The Paris agreement... sets out very clearly that the suspension of conversion and uranium enrichment processing continues until there is a long term agreement under the Paris agreement," Mr Straw told the BBC.
"It's now a matter for the Iranian government to decide whether what we outlined today, in outline, not in any sort of detail, is sufficient for them to continue with the Paris agreement," he said.
"We believe that we could reach a reasonable agreement within a reasonably short time," the chief Iranian nuclear negotiator said.
Mr Rohani later told CNN Iran insisted on producing nuclear energy for peaceful purposes in order to maintain its independence and not have to extend its hand to others.
Earlier, Iranian President Khatami said the Europeans had to understand the Iranian position and its "inalienable right" to nuclear power.
"We will definitely implement our decision even if our friends fail to come to an understanding," Mr Khatami said.
In the meantime, pressure within the US for unilateral action is building.
Both houses of the US Congress have bills calling for tighter economic sanctions and cuts to foreign aid for countries whose businesses invest in Iran.