to be on the verge of

• 在国难临头的时候

  be on the verge of a national disaster

• 大祸临头。

  Be on the verge of a calamity.

• 灾难临头。

  Calamity hanging over one's head.

• 死期临头

  be on the verge of death

• 事到临头要沉住气

  stay calm when facing a challenge