Translation of "Negotiator" in Japanese

We have a good negotiator on the staff.

スタッフに交渉事がうまいのがいます。

Dan, an FBI negotiator, tried to talk to Linda.

FBI交渉人のダンは、リンダに話そうと試みた。

He seems like a softy on the surface, but at the core he's got an iron will that makes him an extremely tough negotiator.

見た目には優しそうだけど、彼って皆から外柔内剛の結構なタフネゴシエータと言われているよ。