Secretary of State John Kerry and his Iranian counterpart Mohammad Javad Zarif wrapped up three days of "intense" nuclear negotiations in the Swiss lakeside town of Montreux on Wednesday with still no deal, as a March 31st deadline for a framework agreement looms.
"We've made some progress from where we were and important choices need to be made," Kerry told reporters after the talks, with a senior State Department official adding that "tough challenges" had yet to be resolved.
Zarif sounded more optimistic, telling Iranian news agency ISNA that "despite existing differences, a final deal is not too far off."
But he warned that the thorny issue of sanctions, which Iran wants lifted, risked torpedoing the deal.
"The Western countries, and especially the United States, must decide whether they want a nuclear deal or to continue the sanctions," he said.
Speaking a day after Israeli Prime Minister Benjamin Netanyahu stridently criticized an agreement he said would not stop Iran from getting a nuclear bomb, Kerry stressed that the purpose of negotiations was to "get the right deal, one that can withstand scrutiny".