By Jan Strupczewski and Kate Abnett STRASBOURG (Reuters) -The European Union’s chief executive on Wednesday proposed a phased oil embargo on Russia, sanctions on its top bank and a ban on Russian broadcasters from European airwaves in its toughest measures yet to punish Moscow for its war in Ukraine. The EU’s sixth round of sanctions, if agreed by member states, would be a watershed for the world’s largest trading bloc, which is dependent on Russian oil and gas and must find alternative supplies just as energy prices are spiking. Reluctance to deliver sanctions that will hurt EU economies as w…