SHANGHAI -- Apple on Friday replied to an inquiry from the Shanghai Consumer Council over the slowing down of older iPhones after iOS updates to offset battery performance.

The company said an upcoming version of Apple's mobile iOS will allow iPhone owners to make the decision between their iPhone's speed and battery condition.

The update will allow users to check the health of their battery and choose whether to turn off the part of the iPhone software that slows it down to preserve its battery life.

Tang Jiansheng, deputy secretary-general of the consumer council, said Apple needs to let consumers know that the system update could slow down their iPhones and leave the choice to consumers.

The council will keep a close eye on the issue, Tang added.

On Monday, the consumer council said it had sent a letter of inquiry to Apple over the slowing down of older iPhones after iOS updates, demanding a reply before Friday.

The council demanded to be informed of the cause of the performance issues and remedy measures as well as complete information regarding the interests of consumers.

The council said it has received 2,615 complaints about Apple products and services last year, compared with 964 complaints in 2015.

In late December, Apple apologized for the slowing down of iPhones with older batteries amid lawsuits and consumer outrage. It said the company will cut the price of out-of-warranty iPhone battery replacements from late January to December 2018.