短语讲解：

1. Others expected to take part in the talks are the “P5 plus one” nations.

take part in 参加
例句：Are you going to take part in the first experiment?
你们会参与首次实验吗?

2. Other countries involved in the negotiations want sanctions to be removed in steps over time.

involve in 使参与[陷入，牵扯到]
例句：I do not want you involve in my work problems.
我工作上的问题不想把你也牵扯进来。

3. And he demanded that sanctions be lifted upon signing the deal instead of in stages.

instead of 代替…， （是…）而不是…
例句：A spirit lamp burns spirits instead of oil.
酒精灯里点的不是油而是酒精。