The EU's foreign policy chief and Iran's top nuclear negotiator have met for talks in Vienna, with both sides describing them as "constructive".
Iran says there should be no preconditions on negotiations
The EU's Javier Solana and Iran's Ali Larijani are thought to be trying to find common ground for negotiations on Iran's nuclear programme.
They will meet again on Sunday, both sides confirmed.
Tehran has rejected accusations it is seeking a nuclear bomb, and refuses to suspend uranium enrichment.
It says there should be no such preconditions on negotiations over its nuclear programme, which it says is solely for power generation.
The US on Friday said it hoped the UN Security Council will begin work on a draft resolution authorising sanctions against its long-time foe next week, after Iran ignored a UN-imposed deadline to suspend enrichment.
But other powers have expressed doubt that sanctions would prove effective against the world's fourth-largest oil exporter.