短语讲解：

1. Also Tuesday, U.S. President Barack Obama said that the United States would “walk away” from a possible nuclear deal with Iran if he is not certain it would block Iran’s path to building a nuclear weapon.

deal with 处理
例句：I have a huge pile of letters to deal with.
我有一大堆信件要处理。

2. The international gathering will take place in December in Paris.

take place 发生
例句：Earthquakes take place far underground.
地震则发生在地球的极深处。

3. He said China will aim to reduce its emissions by at least 60 percent by 2030 from 2005 levels.

at least 至少
例句：For that day at least he lost heart.
至少这一天他是垂头丧气的。