World powers and Iran have released a joint statement at the talks in Lausanne, announcing a preliminary deal. It said enough progress had been reached to continue the negotiations until a final deadline on June 30.
Reading out a joint statement, EU foreign policy chief Federica Mogherini says a "decisive step" has been achieved and that "key parameters" had been agreed.
She said the country's enrichment capacity would be reduced and that no fissile material would be kept at the Fordo centrifuge site. The same release was read subsequently in Farsi by Zarif.
Mogherini had tweeted ahead of the press conference that there was "good news."
Zarif said that solutions had been found.
The officials were unable to confirm that a deal had been reached at the marathon talks, which aim to reach a preliminary political agreement before a final deal is reached by June 30.
But Germany's foreign ministry said on Twitter that agreement has been reached on framework for a final deal on Iran's nuclear program.
The joint statement would wrap up eight days of marathon talks, extended after a deadline of midnight on Tuesday.
The United States, Russia, Great Britain, Germany, France and Chine hope to curb Iran's nuclear technologies that could be used to produce weapons. Iran denies such ambitions but is negotiating because it wants a lifting of economic sanctions.
jil/rc (Reuters, AFP, dpa)