Ayatollah Ali Khamenei spoke at the mausoleum of the founder of the Islamic Republic, Ayatollah Ruhollah Khomeini, at a ceremony marking the 23rd anniversary of his death.
Khamenei rejected as “lies” accusations by the US and its allies that Iran is seeking to develop nuclear weapons.
He also called Israel Iran’s number one enemy.
Iran is engaged in talks with six world powers over its nuclear programme.
The six have demanded that Iran stop enriching uranium to levels they say could be upgraded to weapons-grade material more quickly.
Tehran says recently toughened Western sanctions must be lifted in exchange.