Negotiators face a June 30 self-imposed deadline.
"Freezing Iran`s research and development for a long time, like 10 or 12 years, is not acceptable," Khamenei said, according to Reuters. "All financial and economic sanctions imposed by the U.N. Security Council, the U.S. Congress or the U.S. government should be lifted immediately when we sign a nuclear agreement."
While he said he trusted his negotiating team, he also ruled out inspections of Iranian nuclear sites in military facilities.
"Inspection of our military sites is out of the question and is one of our red lines," he said.
U.S. officials have said Iran agreed in April that the final deal would include allowing inspectors with the United Nations nuclear watchdog, access to sites where nuclear activity is suspected and a halt to certain nuclear activities. Secretary of State John Kerry and other senior Western diplomats have also said that the lifting of sanctions would occur gradually, as Iran implements the deal.
These lingering differences represent the main sticking points facing negotiators.
They`ve apparently agreed on other aspects of the deal, such as to modify the Arak nuclear plant still under construction, to limit the number of centrifuges used to process nuclear fuel and to cap the stockpile of Iran`s low-enriched uranium, which could be used to fuel a reactor or processed further for weapons.
Iran says its nuclear program has peaceful aims, but the United States and other Western nations suspect its ultimate goal is to produce nuclear weapons.
State Department spokesman John Kirby said earlier Tuesday that "any deal must provide the access that (international) inspectors need to verify Iran`s compliance with the ultimate deal that`s reached."
The deal is still being negotiated, Kirby said. "But everybody, including the Iranian delegation back ... agreed that the (international inspection agency) will and must have the access it needs to verify compliance."
Aaron David Miller, a former Middle East peace negotiator and now vice president at the Woodrow Wilson International Center for Scholars, suggested on his Twitter account that Khamenei`s speech was bluster in advance of the deadline.
"How Do We Know Iran Deal Coming?," he wrote on his Twitter account. "Iranian Supreme Leader pushes unreasonable demands as end game nears."
A day earlier, Iranians Foreign Minister Javad Zarif said if there`s political will on all sides, there`s a "good possibility" that a deal will be reached "by the deadline or a few days after the deadline," the Associated Press reported.
Speaking to Iranian state TV, Zarif said said all sides should avoid "excessive" demands.
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