By Francesco Guarascio and John Chalmers STRASBOURG (Reuters) -The European Union’s executive on Wednesday proposed the toughest package of sanctions yet against Moscow for its war in Ukraine, but several countries worried about the impact of cutting off Russia oil imports stood in the way of agreement. The sixth round of measures, announced by European Commission President Ursula von der Leyen, included sanctions on Russia’s top bank and a ban on Russian broadcasters from European airwaves, as well as the embargo on crude oil in six months. The EU depends on Russian oil and gas, and faces the…