BBC news 2009-11-26 加文本

is to表示将来时，和be about to相似。

be to 表示客观安排或受人指示而做某事。
　　 be going to 表示主观的打算或计划。

　I am to play football tomorrow afternoon.　　 (客观安排)
　I'm going to play football tomorrow afternoon. (主观安排)

2. It’s thought he will commit in excess of 30,000 additional troops to the fight in Afghanistan and lay out how he intends in his words, to finish the job.

lay out陈设; 展开

例句：She laid out all her new clothes on the bed.
      她把她所有的新衣服都摊开在床上。

设计

例句：Our plan must be well laid out before we begin to work.
      我们在开始工作之前, 必须制定好计划。

〈非正〉花钱, 花力气

例句：He has laid out all his strength and is weary.
       他使出了全部气力, 非常疲倦。

3.Mr. Obama hopes to be in office for two four-year terms and he says he wants to complete the Afghan mission before he steps down.

step down走下,逐步减低,辞职,下台

例句：The manager had to step down on account of poor health.
      那位经理由于身体不好, 只能辞职不干。

step up走近,逐步增加,提升,提高

例句：He has stepped up into the management of the firm.
      他已升入公司的管理部门。

      When John found he was going to be late, he stepped up his pace.
      约翰发现要迟到了, 就加大步伐。

4.While they fall short of a full freeze, we believe the steps announced by the prime minster are significant and could have substantial impact on the ground.

fall short of不足,缺乏,达不到,不符合

例句：This month we may fall short of our goals.
      这个月我们可能无法达到我们的目标。