World Bulletin / News Desk

A senior Iranian military official welcomed Thursday what he said was the "strong decline" of the United States, during celebrations marking the start of the 1979 US embassy siege.

"America is no longer number one and the first power of the world," deputy Revolutionary Guards commander Hossein Salami told thousands gathered outside the former US mission in Tehran.

"America's political will can no longer manage political and military development in... the world of Islam. America's political power has strongly declined."

The crisis severed US-Iranian diplomatic ties for decades, but Tehran last year clinched a deal with world powers to curb its controversial nuclear programme in exchange for an easing of economic sanctions.

Protesters on Thursday chanted the traditional rallying cries of "Death to America" and "Death to the House of Saud", in reference to Iran's regional rival Saudi Arabia.

But the US remains Iran's main enemy, and Tehran and Washington back opposing sides in several regional conflicts, including Syria and Yemen.

"Our fight with the Americans will continue" Salami said. "Pursuing our ideals in the world of Islam and in Iran, we will recognise no stopping point or red line.

He also warned the US not to criticise Iran's ballistic missiles, calling its system "the real centre of our power (that) must be strengthened."