Iran and six world powers have announced they have agreed a plan meant to produce a comprehensive deal that reduces concerns about Tehran's nuclear ambitions, with officials of both sides describing their plans as "very productive".
In a joint statement, they said negotiations would resume in Vienna on March. 17.
She added that it "won't be easy, but we've gotten off to a good start".
The talks also involved Iranian foreign minister Mohammad Javad Zarif with officials from the US, UK, Russia, China, France and Germany.
Expectations of major progress from the three days of talks in Austria were modest because the two sides have widely differing demands.
The six nations want Tehran to agree to significant cuts in its nuclear programme to reduce concerns it could be turned quickly to weapons use.
Iran is opposed, saying it has no interest in such weapons, but the six powers say Tehran must come to an agreement if it wants a full end to sanctions crippling its economy.