TEHRAN, July 23 (Xinhua) -- Extension of nuclear talks is an indication of a "political will" on both sides toward reaching a final agreement, Iranian Foreign Ministry spokeswoman Marzieh Afkham said here on Wednesday.

The next four months are an extension of the course which started in Geneva last November, Afkham said, adding that in the recent Vienna talks, "the core issues around Iran's nuclear program were discussed and negotiations became more complicated and more difficult."

"Now, there is a political will for continuation of talks in the form extending the Joint Plan of Action" sealed in Geneva last November, she said at her weekly press conference.

As for the time and venue of upcoming meeting between Iran and the P5+1 group, including the United States, Britain, France, China, Russia plus Germany, the Iranian spokeswoman said no date and venue have been decided yet, but early September has been proposed for the next meeting.

Iranian nuclear talks would be extended for another four months till November 24, EU foreign policy chief Catherine Ashton and Iranian Zarif said Saturday in a joint statement, which came only one day ahead of the deadline for a final and comprehensive agreement on Iran's nuclear program.

The interim deal, which took effect on January 20, was designed to buy time for negotiations. Under the deal, Iran would suspend some sensitive nuclear activities in exchange for a limited sanction relief.