"The plans of the arrogant powers, led by the United States, in the Middle East have collapsed, especially in Palestine [PNA], Iraq, and Lebanon," Iranian television quoted Khamenei as saying.
He called on Muslims all over the world to stand up to the "arrogant powers" that are striving to ferment interethnic and communal discord among the followers of Islam.
He said despite the long-running "intrigues and plots by its enemies," Iran is becoming stronger every day.
A senior aide to Iran's supreme leader said Thursday the U.K.'s intrusion into Iran's territorial waters was an attempt by the West to test the republic's defense capabilities.
Iran detained 15 British Navy personnel in the Gulf March 23 for allegedly violating its maritime border with Iraq. Britain has insisted the servicemen were in Iraqi waters under a UN mandate, and were returning in dinghies to HMS Cornwall after patrolling oil platforms.
"By trespassing into our country's territorial waters, the occupation forces in Iraq sought, among other things, to test Iran. But considering Iran's political and military wisdom, they met with a firm rebuff," said Ali Akbar Velayati, international affairs advisor to Iran's Supreme Leader Ayatollah Ali Khamenei
He said that Iran, like the Islamic world as a whole, "is not afraid of Western power."
"Muslims must know that they can stand up to the strongest enemies of Islam," he said.
The 15 British Navy personnel, released by Iranian authorities Wednesday after almost two weeks in custody, returned to the United Kingdom Thursday.
