TEHRAN -- Supreme Leader of the IslamicRevolutionAyatollah Seyed Ali Khamenei said on Sunday thatthe United Statesmakes every effort to block Iran's economicdevelopment and progress.In reaction to the US hue and cry over Iraniannuclear facilitiesto generate electricity for modernizing sociallife, the SupremeLeader said that Iran has never violated theinternational commitmentsand will never back down on the Islamic criteriaand ethicalrequirements.In a meeting with several thousand universitystudents andteachers membering the Basij (volunteer forces),the Supreme Leadersaid that Iran insists on its own distinct rightsin the internationalcommunity and proceeds with its scientificprogress."The United States has designs for every class ofIranian societyespecially for the academics who, thank God, havemade great stridesin the field of science and technology. By makingaccusation againstIran, the US wants to play down the socialprogress the Iranian nationhas achieved in the past 24 years," the SupremeLeader said.Referring to the US threats to attack Iran, theSupreme Leadersaid that the US threats is not something new. TheUS has embarked onsystematic threats against Iran from the morrow ofvictory of theIslamic Revolution, said the Supreme Leader."The Iranian nation will defend its dignity andachievements andthe Basij (volunteer forces) is the well-organizedgrassroot defensestructure present both in the academic centers andthe battlefield,"the Supreme Leader said.The Supreme Leader ruled out the US threatsagainst Iran and saidthat the threats are rooted in animosity emanatingfrom the overthrowof the US-backed puppet regime from Iran andputting an end to thetwo-century record of colonialism in the countryby the IslamicRevolution.