Iran's supreme leader Ayatollah Seyyed Ali Khamenei said Sunday that the UN nuclear watchdog would lose its legitimacy if it folds under pressures exerted by the United States over Iran's nuclear program, the local Press TV reported.

"Some attempts and reports by the International Atomic Energy Agency (IAEA) prove that this international body is not acting independently," Press TV quoted Khamenei as saying.

"The IAEA should not be under the pressure of the United States and some other countries since such unilateral moves will break trust in the agency and the United Nations," he said, adding that "It will also damage the reputation of such international bodies."

In a confidential report which was leaked out earlier this month, the Vienna-based IAEA said it was concerned about possible activities in Iran to develop a nuclear payload for a missile.

The United States and its Western allies have been accusing Iran of secretly developing nuclear weapons under the disguise of a civilian program. Iran has denied the accusation and stressed its nuclear program is only for peaceful purposes.