Iran's supreme leader Ayatollah Ali Khamenei reiterated on Wednesday, Oct 8, his country's "red lines" in negotiations with world powers over its controversial nuclear program due to resume next week in Vienna., according to AFP.

Khamenei's intervention came as both the United States and EU confirmed that U.S. Secretary of State John Kerry and EU foreign policy chief Catherine Ashton would meet in the Austrian capital with Iranian Foreign Minister Mohammad Javad Zarif.

Ashton will first hold bilateral talks next Tuesday with Zarif, as is customary ahead of each round of nuclear negotiations, and a three-way meeting is to be held the next day on October 15, her spokesman Michael Mann said.

Top-level U.S. diplomats would also meet with their Iranian and EU counterparts on October 14 ahead of the trilateral ministerial talks, a U.S. official said, also confirming the trilateral talks.

"Our focus... is determining whether it's possible to reach an agreement by November 24 that effectively closes down Iran's pathways to nuclear materials for a nuclear weapon," State Department spokeswoman Jen Psaki told reporters, according to AFP.

U.S. officials "continue to believe that there is still adequate time to work through these issues and arrive at a comprehensive agreement that will give the international community assurances that Iran will not acquire a nuclear weapon," she added.

An infographic published on Khamenei's official website outlined 11 points to be observed by negotiators before Iran will sign an accord.

One of the stipulations includes "the absolute need for Iran's uranium enrichment capacity to be 190,000 SWU (Separate Work Units)" -- close to 20 times its current processing ability. Iranian officials say this is needed to produce fuel for its Bushehr reactor, which is being provided by Russia until 2021.

The U.S. and other Western states, however, want Iran to decrease its enrichment capability.

"Fordo, which cannot be destroyed by the enemy, must be preserved," the text on Khamenei's website said, referring to the uranium enrichment site built under a mountain 100 kilometres (60 miles) south of Tehran.

"The work of nuclear scientists should in no way be stopped or slowed," the text said, adding Iran had the right to pursue nuclear "research and development".