Gen. Hossein Salami, the Guard's deputy leader, said on state TV that allowing the foreign inspection of military sites is tantamount to "selling out".
"We will respond with hot lead (bullets) to those who speak of it," Salami said. "Iran will not become a paradise for spies. We will not roll out the red carpet for the enemy."
Iran and six world powers -- the US, the UK, France, Germany, China and Russia -- have reached a framework agreement to curb Tehran's nuclear programme in return for lifting sanctions, and hope to strike a final deal by June 30.
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.
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The fact sheet said Iran has agreed to implement the Additional Protocol to the Non-Proliferation Treaty, which would grant the IAEA expanded access to both declared and undeclared nuclear facilities.
"It means humiliating a nation," Salami said on state TV. "They will not even be permitted to inspect the most normal military site in their dreams."
Iran allowed IAEA inspectors to visit the Parchin military site in 2005 as a confidence-building measure, but denied further visits, fearing espionage.
Western nations have long suspected Iran of secretly pursuing a nuclear weapons capability alongside its civilian programme. Tehran denies such allegations, and insists its nuclear programme is entirely peaceful.