The European Union's foreign policy chief, Catherine Ashton, has said talks with Iran on its nuclear programme were "constructive and useful".
The next round of talks with Tehran will take place in Baghdad on 23 May, she said.
The first discussions between Iran and six world powers for 15 months have been taking place in Istanbul.
Iran says its nuclear programme is peaceful, but critics suspect it of seeking to develop weapons.
Speaking at the end of Saturday's talks between the six countries - the US, UK, France, China, Russia and Germany - and Iran, Baroness Ashton said that future talks would be guided by the "principle of a step-by-step approach and reciprocity".
She said that Iran has the right to a peaceful nuclear programme, and that the nuclear Non-Proliferation Treaty must be a "key basis" for future talks.
Baroness Ashton said she and the Iranian chief nuclear negotiator, Saeed Jalili, were united in their desire to pursue a long-term solution to the problem.
Mr Jalili described Saturday's talks as being based on co-operation and "very successful".
BBC News - Ashton hails Iran nuclear talks
This is indeed good news - a peaceful approach is the best way forward - now the war mongers go home and enjoy the break...
The next round of talks with Tehran will take place in Baghdad on 23 May, she said.
The first discussions between Iran and six world powers for 15 months have been taking place in Istanbul.
Iran says its nuclear programme is peaceful, but critics suspect it of seeking to develop weapons.
Speaking at the end of Saturday's talks between the six countries - the US, UK, France, China, Russia and Germany - and Iran, Baroness Ashton said that future talks would be guided by the "principle of a step-by-step approach and reciprocity".
She said that Iran has the right to a peaceful nuclear programme, and that the nuclear Non-Proliferation Treaty must be a "key basis" for future talks.
Baroness Ashton said she and the Iranian chief nuclear negotiator, Saeed Jalili, were united in their desire to pursue a long-term solution to the problem.
Mr Jalili described Saturday's talks as being based on co-operation and "very successful".
BBC News - Ashton hails Iran nuclear talks
This is indeed good news - a peaceful approach is the best way forward - now the war mongers go home and enjoy the break...