Iran’s supreme leader Ayatollah Ali Khamenei on Wednesday ruled out allowing nuclear inspectors to visit military sites or to question scientists, state media reported.

“We have already said that we will not allow any inspections of military sites by foreigners,” the official IRNA news agency quoted him as saying.

“They also say that we must allow interviews with nuclear scientists. This is interrogation. I will not allow foreigners to come and talk to scientists who have advanced the science to this level,” Khamenei said.

Other Iranian officials have repeatedly claimed that inspectors would not be given freedom of access to nuclear facilities — directly contradicting US officials who tout comprehensive inspections as being a key element of a final deal.

Khamenei’s statements came as experts from Iran and six world powers prepared to launch a new round of negotiations focused on reaching a deal that curbs Iran’s nuclear program.

Diplomats said ahead of Wednesday’s meeting that progress is being made but significant gaps remain on a main document and technical annexes ahead of an end-of-June deadline.

Iran’s team is led by Deputy Foreign Minister Abbas Araqchi. EU official Helga Schmidt is heading the other side. Senior officials from the US, Russia, China, Britain, France and Germany may join in later.

The deal aims for strict limits on Iranian nuclear capabilities that could be used to make weapons. Tehran denies any interest in such arms but is negotiating for a lifting of sanctions.

The diplomats demanded anonymity because they are not authorized to discuss the talks.

A framework agreement — reached at the beginning of April and set to be finalized by June 30 — called for a scaling back of Iran’s uranium enrichment program along with comprehensive inspections of its nuclear facilities to ensure it is not developing atomic weapons. In return, Iran demanded that global sanctions that have crippled its economy be lifted.

A fact sheet on the framework accord issued by the State Department at the time said Iran would be required to grant the UN nuclear agency access to any “suspicious sites.”

Iran has questioned that and other language in the fact sheet, notably that sanctions would only be lifted after the International Atomic Energy Agency has verified Tehran’s compliance. Iran’s leaders have said the sanctions should be lifted on the first day of the implementation of the accord.

Less than a week after the framework agreement was reached, Iranian Defense minister Brigadier General Hossein Dehgan made it clear that international inspectors would not be granted access to the state’s military sites under the terms of the deal.

“No such agreement has been reached and basically, visiting military centers are among the red lines and no visit to these centers will be allowed,” Dehgan said, according to Iranian media reports quoting a Defense Ministry statement.

Later that month Gen. Hossein Salami, deputy commander of Iran’s Revolutionary Guard also said that inspectors would be barred from military sites under any nuclear agreement and that allowing such check ups would be tantamount to “selling out.”

Those opposing the deal, including Prime Minister Benjamin Netanyahu and other top Israeli officials, have criticized the terms of the framework agreement for not completely removing Iran’s ability to enrich uranium or to work towards producing a nuclear weapon.