Ayatollah Ali Khamenei, who has the final say in all matters of state in Iran, praised the powerful Revolutionary Guards for their "show of advanced and precise missiles" in recent tests that drew Western criticism.
"In this jungle-like world, if the Islamic republic seeks negotiations, trade and even technology and science, but has no defence power, won't even small countries dare threaten Iran?" Khamenei said in remarks published on his official website.
"Our enemies are constantly enhancing their military and missile capabilities and given this how can we say the age of missiles has passed?"
They also came a day after the United States, France, Britain and Germany said Iran's recent ballistic missile tests violate UN Security Council resolutions.
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The same four countries, along with Russia and China, reached the historic agreement with Iran last year that saw Tehran scale down its nuclear programme in exchange for the lifting of sanctions.
Iran has twice tested ballistic missiles since the July 14 deal, prompting Western condemnation and new US sanctions.
He said those who believe only diplomacy is the key to Iran's future are acting out of "ignorance or treason".