The Prime Minister, Tony Blair was set to take part in a video conferencing experiment linking schools in 20 countries on Tuesday.

He was due to answer questions from pupils in South Africa, Iceland and the UK as part of the Global Leap 2000 initiative.

The project aims to link up schools across the world in a 16-hour distance learning event to be witnessed over the internet by more than 1,000 people.

It has been devised by teacher Mike Griffith at Arbour Vale Special School in Slough, Berkshire and IT specialists PictureTel.

During Tuesday, there will be 21 distance-learning events, each hosted by an individual school or institution, linking directly with four others and available remotely to many more.

UK events are to include a lesson at London's Science Museum about Amy Johnson's historic London to Darwin flight, and a maths lecture given by Cambridge University academics.

Events planned in other countries include an expedition into a South African game reserve, and a science experiment with Nasa.

Mr Griffith, who began planning the project 18 months ago, said it pointed the way ahead to new educational opportunities.

"Many schools have the technology for video-conferencing, but aren't aware of the possibilities for using it.

"What it does is to make lessons being given in one school, and educational experiences, available around the world."