Republican Sen. John Thune said Wednesday on CNBC that he wants to know why Apple hasn't been more "transparent" about why the company chose to deliberately slow the performance of batteries in some older iPhones.

Thune, who chairs the Commerce, Science and Transportation Committee, requested answers from the company in a letter released Wednesday. Apple is supposed to respond by Jan. 23.

The South Dakota Republican said he isn't "ruling anything out" should Apple fail to adequately answer his questions.

"We could have a hearing at some point and elevate this further," Thune told CNBC's " " on Wednesday.

Apple disclosed in December that it had been slowing down batteries in older iPhones to save components from overuse without notifying users. It apologized to customers and dropped the price of a battery replacement to $29.