Tehran: A senior Iranian cleric said the United States should apologise to Iran after a UN nuclear watchdog report revealed that Tehran had been telling the truth about its nuclear plans.

Iran's influential Ayatollah Ahmad Khatami said Iran would not back down "even one iota from defending its basic rights" in pursuing nuclear energy.

"America must apologise to the great Iranian nation for lying to the world's public opinion," Khatami told Friday worshippers in a sermon broadcast live on state radio.

The International Atomic Energy Agency (IAEA) said in its report on Thursday that Iran had made important strides towards clarifying past nuclear activities.

Khatami said the IAEA report had confirmed "the facts that Iran was stressing during the past four years", but that it also contained inaccuracies.

"This was a relative victory because some parts (of the report) are still incorrect," he said.