U.N. Secretary-General Ban Ki-moon has called for Iran's nuclear dispute with the West to be resolved through negotiations rather than military action.

Mr. Ban's spokesman said Thursday the U.N. chief believes diplomacy is the “only way” to settle the issue. Recent reports in the Israeli media say Israel's government has been considering a military strike on Iran's nuclear sites to stop what Western powers suspect is an Iranian program to develop nuclear weapons.

The International Atomic Energy Agency released a report Tuesday saying it has “credible” evidence of Iranian efforts to design a nuclear weapon. Iran has rejected that report and insisted that its nuclear program is peaceful. U.N. spokesman Martin Nesirky says Mr. Ban believes the “onus is on Iran” to prove the peaceful nature of that program.

Iran's Supreme Leader Ayatollah Ali Khamenei said Thursday Iran will respond to any military strike by Israel or its main ally the United States with “strong slaps and iron fists.” But, in a nationally-televised speech to military cadets in Tehran, he also said Iran does not intend to start a conflict.

The comments were the strongest yet by Iran since Israeli officials began making references to potential military action against the Iranian nuclear program in recent days.

Iranian President Mahmoud Ahmadinejad said Wednesday Iran will not retreat “one iota” from its nuclear activities.

Israel responded to the IAEA report by calling on the international community to stop Iran from gaining nuclear weapons and endangering world peace. Israel is widely believed to have the only nuclear arsenal in the Middle East. It sees a nuclear-armed Iran as a threat to its existence.

Britain, France and Germany warned that Iran faces additional sanctions if it refuses to address international concerns about its nuclear work. But, Russia's foreign ministry said Thursday Russian and Chinese diplomats who met in Moscow agreed that new sanctions “will not lead to the desired result” of resolving the Iranian nuclear dispute.

The U.N. Security Council has passed four sets of sanctions on Iran for refusing to stop nuclear activities that have both civilian and military uses.