Apple is said to be working on curved screens for future versions of the iPhone, as well as sensors that can detect different levels of pressure.

The curved models are set to have larger screen sizes of 4.7 inches and 5.5 inches, reports Bloomberg.

It says a source familiar with the plans believes a release date in the second half of next year is likely.

Samsung released a curved phone, the 5.7-inch Galaxy Round, last month - but the handset is currently available only in South Korea.

LG also revealed a similar device with a 6-inch screen, called the G Flex.

Customer interest in the flexible curved-screen phones - which are said to be more durable - remains to be seen, but Apple appears to see the potential.

The phones are also marketed as more ergonomic and better for watching videos and playing games.

Apple is also working on screen sensors that can distinguish between light and heavy touches, Bloomberg reports.

However, it is thought they will not be ready in time for the next iPhone release.

An Apple spokeswoman declined to comment on the rumours.

The technology giant released its last update to the iPhone in September, bringing out a flagship 5S model and the cheaper 5C - designed to target emerging markets.

Despite selling well, some experts have criticised the firm for lacking innovation and failing to lead the market since the death of co-founder Steve Jobs.

The company has also seen greater competition from Android-powered phones and tablets, made by the likes of Samsung and Google.