Iranian Supreme Leader Ayatollah Ali Khamenei has called the notion of an Iranian effort to develop nuclear weapons a fabrication by the West to portray Iran as a threat.
Addressing military commanders on April 19, Khamenei said the United States -- not Iran -- presented the real danger.
"They created the myth of nuclear weapons so they could say the Islamic Republic is a source of threat. No, the source of threat is America itself," he said.
The comments come as negotiations between Iran and world powers on Tehran's nuclear program will resume in Vienna next week.
The United States, Russia, China, Britain, France, Germany, and Iran have set a June 30 deadline for a deal to restrict Tehran's nuclear activities, which Western nations fear are aimed at developing nuclear weapons or a weapons capability, in exchange for sanctions relief.
Khamenei, who has the final say on all state matters, has said he neither supports nor opposes a framework deal reached this month, adding that he will wait until it is finalized.
Khamenei and other Iranian officials have said that sanctions on Iran must be lifted as soon as the final agreement is concluded.
But the United States United States has said that any removal of sanctions on Iran will be gradual.
In the television speech on April 19, Khamenei also said world powers are threatening Iran "militarily" and urged Iran's armed forces to increase their "defensive preparedness"
"Even if they did not make these overt threats, we would have to be prepared," he said.
His comments were seen as a response to General Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff, who said last week should ongoing diplomacy with Iran fail, "the military option...to ensure that Iran does not achieve a nuclear weapon is intact."
Khamenei also criticized U.S. support for Saudi-led air strikes that are targeting Shi'ite Huthi rebels in Yemen.
"Today these tragic events are happening in Yemen and the Americans are supporting the oppressor," he said.
Iran denies aiding the Huthis who seized the Yemeni capital, Sanaa, last year and took control of other part of the country.
The Saudi-led campaign, in which Iran and the West have backed opposite sides, began during the last round of nuclear talks some four weeks ago.
Shortly before Khamenei's address, a senior commander in Iran's Revolutionary Guard says the country's military sites would not be open to foreign inspection under any nuclear agreement with world powers.
Hossein Salami, the Guard's deputy leader, said allowing the foreign inspection of military sites amounts to "selling out."
A fact sheet on the framework accord issued by the State Department said Iran would be required to grant the UN nuclear agency access to any "suspicious sites."
Iran, which insists its nuclear program is for purely peaceful purposes, has repeatedly said its military sites will not be open to inspection.