An aide to Jalili said the talks would resume even if the timing and venue were still undecided, but Ashton said further talks depended on a more constructive approach from the Iranian side.
Chinese Assistant Foreign Minister Wu Hailong told Xinhua the Iranian nuclear issue was a complicated and sensitive topic and it was hard for all parties to seek a comprehensive solution through a few dialogues.
The Chinese diplomat said all parties should make further efforts to continue dialogue and negotiation while taking pragmatic and flexible attitude and continuing confidence building.
The West suspects Iran wants to develop nuclear weapons while Tehran says its atomic energy program is peaceful.
Turkey said Saturday that it was ready to contribute in any way to a peaceful resolution to the Iranian nuclear talks.
Although no agreement was reached, "we are glad that both sides have left the door open for future negotiations," said Turkish Foreign Ministry spokesman Selcuk Unal in a statement at a press conference after the talks.
"We have been defending that this issue should be resolved by diplomatic means only since the beginning," Unal said, adding "the Istanbul meeting is just a culmination of this attitude."