The United States on Tuesday approved a $2.2 billion sale of advanced battle tanks to Bahrain, a Gulf Arab ally once under an arms embargo over a crackdown on pro-democracy protests. The State Department said it had notified Congress it is ready to sell 50 M1A2 Abrams tanks, generally used for ground warfare, to the small island nation which has tense relations with nearby Iran. “The proposed sale will improve Bahrain’s capability to meet current and future threats by providing a credible force that can deter adversaries and provide the capability to participate in regional operations with the…