“The Secretary-General hopes that, in advance of the forthcoming technical and political meetings, the parties strengthen their resolve to quickly achieve a negotiated solution that restores international confidence in an Iranian nuclear program that could be deemed exclusively peaceful,” Ban’s spokesperson said in a statement.

The secretary general called on the six mediators on Iran’s nuclear issue – Britain, China, France, Germany, Russia and the United States – to continue negotiations with Tehran “with renewed intensity and with the utmost flexibility.”

The two-day Moscow talks ended on Tuesday without a breakthrough. The European Union foreign policy chief, Catherine Ashton, who heads the group of mediators, and Russian Deputy Russian Foreign Minister Sergei Ryabkov both said after the talks that there were still “significant differences” between the sides.

The mediators have been trying to persuade Iran to drop its uranium enrichment program, which Western nations suspect is aimed at producing weapons. Tehran insists it needs enriched uranium for peaceful energy generation.

Technical experts from both sides have agreed to convene in Istanbul, Turkey, on June 3, to decide whether there are grounds for further high-level negotiations.