Iran and key world powers have ended their first day of talks on Tehran's nuclear programme in more than a year without a breakthrough.
The talks in Geneva lasted nearly 10 hours and will continue on Tuesday.
On Sunday Iran said it had delivered its first domestically produced raw uranium and would now go into the talks with "strength and power".
Western powers fear Iran may be trying to produce nuclear arms, but Tehran says its programme is purely peaceful.
Iran's top nuclear negotiator Saeed Jalili has been meeting EU foreign affairs chief Baroness Ashton and senior officials from the five permanent members of the UN Security Council - the US, Russia, China, France and Britain - plus Germany.
'Lack of trust'
On Iranian state television, nuclear chief Ali Akbar Salehi said the Geneva talks were for the benefit of the other countries, not Iran.
"We want to create a graceful solution out of the political deadlock for those who have pressurised us," he said.
Analysts say the best outcome that can be hoped for is simply that the two sides agree to hold further meetings.
A source told BBC Iran correspondent James Reynolds, who is in Geneva, that the talks were "constructive and wide-ranging" but each side accepts there is a mutual lack of trust.
Mr Jalili began by raising the car bomb attacks in Tehran last week, in which one of Iran's top nuclear scientists was killed and another injured. Iran blames the bombings on Western intelligence services.
Baroness Ashton condemned the attacks, our correspondent says.
The last Geneva talks, in October 2009, appeared to agree on a breakthrough deal under which Iran would export low-enriched uranium for processing abroad. However, Iran introduced new conditions and the deal foundered.
The UN Security Council has said that until Iran's peaceful intentions can be fully established, it should stop enrichment and other nuclear activities.
Iran is under four sets of UN sanctions over its refusal to heed repeated Security Council ultimatums to suspend uranium enrichment.
The latest UN sanctions, adopted on 9 June, include a ban on dealing with Iranian banks and insurance companies, as well as steps to prevent investment in Tehran's oil and gas sector.
Iran says that as a signatory of the Nuclear Non-Proliferation Treaty, it has the right to enrich uranium for fuel for civil nuclear power.
Recent Wikileaks releases of secret US diplomatic cables also revealed some Arab states calling for military action against Iran's nuclear facilities.
On Sunday, Iran said it had mined and produced its first home-manufactured uranium yellowcake.
Mr Salehi said: "The West had counted on the possibility of us being in trouble over raw material but today we had the first batch of yellowcake [raw uranium] from Gachin mine sent to Isfahan [conversion] facility."
Enriched uranium can be used for fuel in reactors or made into nuclear bombs.
Iran was believed to be running low on its stock of yellowcake, originally imported from South Africa in the 1970s.
Producing it domestically would enable Iran to circumvent the four rounds of increasingly harsh UN sanctions.
White House National Security Council spokesman Mike Hammer said the announcement was not unexpected, as Iran had been trying to develop its own uranium programme for years.
"However... this calls into further question Iran's intentions and raises additional concerns at a time when Iran needs to address the concerns of the international community," Mr Hammer said.