Internet voice and video calls are on the cards for some PlayStation Portable (PSP) owners later this year.

BT said last week that it is developing a software-based Internet telephony package for the portable device. The system will allow users to make voice and video calls across a Wi-Fi network. Later it will be extended to cover calls and messages to PCs, fixed line phones and cell phones, said BT.

The PSP comes built-in with a Wi-Fi adapter. Video calls will require the use of an add-on camera.

BT will roll-out the service in Europe, the Middle East, Africa and Oceania with the support of Sony Computer Entertainment Europe, Sony's gaming division responsible for PlayStation products in territories that use the PAL television colour system.

While the system is planned for roll-out later this year in SCEE territories, it might not turn up in other markets like the Americas, Japan or Asia. That's because the effort is largely led by BT and not Sony, said Satoshi Fukuoka, a spokesman for Sony Computer Entertainment in Tokyo.

Sony is currently trying to make the PSP more attractive to users.

Sales of the PSP have been well below Sony's expectations. The company started the last fiscal year predicting it would ship 12 million of the units but cut the number by a quarter when it became clear that consumers were not buying the PSP at the levels anticipated by the company. At the close of the fiscal year in March Sony had shipped 8.4 million PSPs -- down significantly from the 14 million shipped in the prior year.