step by step;gradually;progressively;per gradus[拉](step by step) 战争～升级 escalation of war/～撤退，～撤销phase out/～到位phase in;phased imple mentation/～加以解决settle sth step by step/～降低生产成本progressively reduce the production cost /～降级de-escalate /～取消phase out/～升级escalate/～缩小，～减少phase down; wind down/～推广gradual popularization/～消除贸易壁垒phased removal of trade barrier