EU foreign-policy chief Catherine Ashton says talks between Iran and six world powers to reach a permanent agreement on Tehran's controversial nuclear program will "move to the next stage" in mid-May.
Ashton made her remarks at the conclusion of two days of talks in Vienna between Iran and Britain, France, Russia, Germany, the United States, and China.
Ashton added that "intensive work" was needed in order to overcome differences in the talks, aimed at signing a long-term accord to curb Iran's nuclear program.
Ashton said the next round of talks will be held in Vienna starting on May 13.
Reuters quoted a Western diplomat as saying there were still "some significant gaps" between the two sides.
A temporary agreement was signed in November but expires on July 20.
Iranian Foreign Minister Mohammad Javad Zarif, who led the Iranian delegation at the talks, insisted that "nothing can be imposed on Iran" regarding its nuclear activities.
Meanwhile, Iran's Supreme Leader Ayatollah Ali Khamenei, who has the final say on all state matters, said Iran "should continue" the nuclear talks with the six powers.
But Khamenei also said that Iranian negotiators should not yield to issues "forced upon them."
He made the comment at a meeting with nuclear scientists in Tehran on April 9 as Iran marked its National Nuclear Technology Day.
Tehran denies accusations that it is seeking a nuclear-weapons capability and wants an end to sanctions that have drastically reduced its oil income and virtually barred it from the international financial system.
The November agreement provided Iran with limited sanctions relief in exchange for a six-month suspension of some nuclear activities, including higher-grade enrichment, that began on January 20.
With reporting by Reuters and AFP