The company said the issue has affected a ‘very limited number’ of users and that it was contacting them to offer a replacement.
The admission will be embarrassing to Apple, which has been criticised in the past for the battery life of its products.
In 2006 it issued a recall for some laptops because some of the batteries were exploding.
The iPhone 5S has sold nine million units already since its launch in September with mixed reviews on the battery life.
Apple spokeswoman Teresa Brewer said: ‘We recently discovered a manufacturing issue affecting a very limited number of iPhone 5S devices that could cause the battery to take longer to charge or result in reduced battery life.
‘We are reaching out to (contacting) customers with affected phones and will provide them with a replacement phone.’
Ironically the iPhone 5 had in the past been praised for having a better battery than the iPhone 4.
In its review of the device, Techradar said if left on standby overnight the battery dropped off by just five per cent.
It also said that it charges ‘phenomenally quickly’ and that it went from zero to full in just over two hours.
Apple has smashed its own records by selling nine million iPhone 5S and iPhone 5C handsets during the first three of the devices going on sale – working out as 125,000 an hour, on average, or 2,083 a minute.
Last year’s iPhone 5 sales topped five million during its opening weekend in September 2012, yet only one handset was available – as opposed to this year’s two
‘This is our best iPhone launch yet more than nine million new iPhones sold a new record for first weekend sales,’ said Tim Cook, Apple’s CEO.
‘The demand for the new iPhones has been incredible, and while we’ve sold out of our initial supply of iPhone 5s, stores continue to receive new iPhone shipments regularly.
‘We appreciate everyone’s patience and are working hard to build enough new iPhones for everyone.’
The iPhone 5S handset claims to offer 10 hours of talk time and 250 hours of standby with a single charge.
The iPhone 5S has sold nine million units
Part of the reason for the improvements could be iOS 7, the new operating system, which is thought to organise apps better.
Techradar did however point out that Internet browsing still chewed up the battery very quickly and that it did not believe Apple’s claims that users got 10 hours surfing on 3G.
The iPhone 5S costs between £549 and £709 new and still has a waiting list after launch because of features like the fingerprint scanner which unlocks the phone.
It is the more expensive version of the iPhone 5C which costs from £469. (Dailymailonline)
