After more than 15 hours of expert-level talks, the United States and other world powers agreed with Iran on Wednesday to move toward a resumption of full negotiations to ensure that Iran’s nuclear fuel enrichment does not turn into a weapons program, a European participant at the talks said.

The Istanbul meeting began Tuesday amid doubts that talks would resume after they stalled last month.

But as of early Wednesday, the participants had reached an agreement to implement the “Moscow plan,” a process that would start with a meeting between a senior European Union official, Helga Schmid, and her Iranian counterpart, Ali Bagheri.

The outcome of that meeting would determine whether full-scale negotiations would follow, said a European diplomat attending the talks, speaking on the condition of anonymity.

Shortly after 1 a.m., the Iranian delegation left the talks without commenting. But one member, as he departed, told a reporter, “We are smiling, and that says it all.”

Israel has threatened a military strike if Iran does not cease enriching uranium to 20 percent — a degree that, while far short of weapons grade, would allow it to produce nuclear weapons in a matter of a year or more.

But with top Israeli military and intelligence figures and senior U.S. officials warning that an Israeli airstrike would only delay the Iranian program for a few years at most, Prime Minister Benjamin Netanyahu agreed to give President Obama a chance to seek a diplomatic solution first.

Political talks were launched here in April and were moved to Baghdad in May, but they stalled in the third round in Moscow in mid-June.

On Sunday, the European Union and the United States introduced a new round of tough sanctions against Iran, including a cutoff of European oil purchases and U.S. sanctions against the Iranian central bank.

Iran denies any intention of developing nuclear weapons.

— McClatchy-Tribune