“Power” in Chinese is 势力 (shìlì).
他试图扩大自己的势力范围。
He tried to enlarge his sphere of influence.
Example sentence from Tatoeba (CC BY 2.0).
Not to be confused with: 视力 (shìlì, eyesight; visual acuity) · 实力 (shílì, strength) · 失利 (shīlì, to lose)