Khamenei, in a speech carried Sunday by state television, said, "We fundamentally reject nuclear weapons and prohibit the use and production of nuclear weapons" and accused the United States of leveling false charges, The Washington Post reported.
"The U.S. officials who claim that the Iranian missiles are dangerous or that we are seeking to produce atomic bombs know themselves that such statements are false," Khamenei said.
The Post reported his remarks came as Iran prepared to hold negotiations with world powers, including the United States, on Oct. 1. Washington and other Western nations believe Iran is using its uranium enrichment program to develop a nuclear weapon, but Iranian President Mahmoud Ahmadinejad says it is merely for peaceful energy use.
The West has proposed tighter United Nations sanctions on Tehran if it doesn't yield more information about its program.
Ahmadinejad is set to speak this week to a gathering of the U.N. General Assembly, the newspaper noted.