U.N. Secretary General Ban Ki-moon communicated to Iranian leaders his strong disapproval of Iran’s rights record and its stand on key issues causing regional and global tensions within hours of his arrival in Tehran to attend the Non-Aligned Movement (NAM) summit Wednesday.

In separate meetings with Iran’s highest leader Ayatollah Sayyed Ali Hosseini Khamenei and President Mahmoud Ahmadinejad, Ban said “concrete” progress was needed to end Tehran’s alleged nuclear weapons ambitions.

Ban called for “steps to address the concerns of the International Atomic Energy Agency and to prove to the world that its nuclear program is for peaceful purposes,” U.N. spokesperson Martin Nesirky was quoted as saying by Al Jazeera.