Iran has hardened its stance less than a week before the deadline for a nuclear deal, with Ayatollah Ali Khamenei rejecting a long-term freeze on nuclear research as it ratified a bill banning access to military sites and scientists.
He also insisted that Iran will only sign a deal if international sanctions are lifted first, which could further complicate the negotiations. The ratified bill, now binding law, calls for all sanctions to be lifted the first day of implementation.
The supreme leader has backed his negotiators amid criticism from hard-liners, but his latest remarks may narrow their room to maneuver ahead of a self-imposed June 30 deadline for a potentially groundbreaking deal with world powers that would curb Iran's nuclear activities in exchange for lifting sanctions.
Iran's constitutional watchdog, known as the Guardian Council, ratified legislation banning access to military sites and scientists, making it binding law, according to state TV.
The bill would still allow for international inspections of Iranian nuclear sites within the framework of the Nuclear Non-proliferation Treaty.
The United States -- which is negotiating the deal with Britain, France, Russia, China and Germany -- has said the sanctions would be gradually lifted as inspectors verify Iran's compliance with the deal.
Speaking Tuesday night in comments broadcast on Iranian state television, Khamenei said demands that Iran halt the research and development portion of its nuclear program constitute "excessive coercion."
"We don't accept 10-year restriction. We have told the negotiating team how many specific years of restrictions are acceptable," Khamenei said. "Research and development must continue during the years of restrictions."
Khamenei said the U.S. is offering a "complicated formula" for lifting sanctions. He said that waiting for the U.N.'s International Atomic Energy Agency to verify Tehran's cooperation would take too long.
"Lifting sanctions can't depend on implementation of Iran's obligations," he said.
Khamenei also said he rejects any inspection of military sites or allowing Iranian scientists to be interviewed. Iran's nuclear scientists have been the targets of attacks, both inside the Islamic republic and elsewhere.
The Americans' "goal is to uproot and destroy the country's nuclear industry," he said. "They want to keep up the pressure and are not after a complete lifting of sanctions."
In a statement Sunday, the U.S. State Department said inspections remain a key part of any final deal.
Western nations have long suspected Iran is covertly pursuing a nuclear weapons capability alongside its civilian program, charges denied by Tehran, which insists its atomic program is for purely peaceful purposes.
Negotiations likely will begin in earnest in the coming days in Europe.
On Wednesday, Iran's official IRNA news agency reported that deputy foreign ministers Abbas Araghchi and Majid Takht-e-Ravanchi had resumed talks with Helga Schmidt, a deputy of European Union foreign policy chief Federica Mogherini. It did not elaborate.