Allegations the Syrian regime used chemical weapons on August 21 are a \"pretext\" to attack the country, Iran\'s supreme leader Ayatollah Ali Khamenei said Thursday. The United States and their allies \"are using the chemical weapon (allegation) as a pretext,\" and \"are saying that they want to intervene for humanitarian reasons,\" said Khamenei, who is a key backer of the Damascus regime US President Barack Obama is seeking Congress\' approval for limited strikes against Syria.