Representatives from Iran and several world powers agreed to restart high-level talks early Wednesday, less than a month after breaking off full negotiations for lack of progress.

The surprise development came after 15 hours of talks between Iran and the five UN security council nations plus Germany, the so called P5+1, in Istanbul, according to a European diplomat quoted by the McClatchy-Tribune news service.

The talks, aimed at curbing the Islamic Republic’s enrichment of uranium to below 20 percent, were cut off in mid-June, with Western officials saying they had failed to make any headway in three rounds of meetings.

Israel, which wants to keep enrichment to below 3 percent, has said the talks are being used as a stalling tactic by Iran. Jerusalem has hinted a military strike could be in the offing should diplomatic initiatives fail.

On Wednesday, low-level technical experts from both sides agreed to adopt the “Moscow plan” for restarting full negotiations, which would begin with a meeting between a senior European official and an Iranian counterpart, who would then decide whether to move forward, according to the report.

While representatives were mostly tight-lipped about what happened behind closed doors, one Iranian representative told the service “We are smiling, and that says it all.”

Another Iran representative, however, said the move was not necessarily a sign of progress.

“The atmosphere is quite mixed,” an Iranian official told the Christian Science Monitor about the meeting. “Both sides want to show that the talks have some outcomes, even if it is [just] to set a date and venue for the next expert meeting.”

Iran had earlier said it wanted a “win-win” in talks.

The development comes just four days after powerful European Union sanctions on Iranian oil went into effect. Iran has admitted that the embargo, together with other sanctions, are taking a toll on the country.