Sony said on Wednesday that it would stop making personal digital assistants for Japan in July, completing its withdrawal from a market hit by multifunctional mobile phones and casting a shadow over the tools' growth potential.

The move was widely expected after the electronics and entertainment conglomerate said last year it would stop selling new handheld digital assistants outside Japan, striking a blow to PalmSource, whose software powers the devices.

A Sony representative said: "The PDA market is being encroached by mobile phones and other mobile devices that can offer similar functions, making it difficult for PDAs to maintain their position in the market."

As devices that largely specialize in organisiing schedules, PDAs have come under heavy pricing pressure, she added.

Sony was the largest PDA maker in the domestic market in 2003, with a 32.1 per cent share by unit shipments, followed by Sharp's 19.5 per cent and Casio's 16.4 per cent, according to research company Gartner.

The decision is the latest in a series of steps by Sony to focus resources on core businesses.

The company said in December it might quit the plasma television business and focus its efforts in the flat-screen TV market on liquid crystal display and rear-projection models, areas where it has a technological edge.

Sony said on its website that the PDA decision did not change the fact that it considered the mobile-terminal business one of its growth pillars.

Sony in December launched the PlayStation Portable handheld game console, which can also play movies and music, in Japan. The machine poses a serious threat to Nintendo, which had dominated the portable game market.