Nuclear materials that could be sold or stolen and fashioned into a nuclear weapon exist in dozens of nations, Mr Obama said in welcoming the other leaders gathered round a gigantic conference table. 目前数十个国家存在着核材料,这些材料可能被出售或被盗,然后改造成核武器,奥巴马在欢迎围坐于巨型会议桌边的其他领导人时说。