The three leading Democratic candidates - Ms Hillary Clinton, Mr Barack Obama and Mr John Edwards - are providing 'mobile updates' to supporters who choose to receive short message service (SMS) updates on their cellphones.

Political observers say this technology, which has been available for a number of years in the US, has yet to be tapped here for political campaigns, which already use a variety of technologies such as e-mail, websites, blogs and online videos.

The use of SMS as an organising tool has been demonstrated in other countries. Some say that text messages helped fuel rallies that led to the ouster of Philippine president Joseph Estrada in 2001; and they may have tipped the balance in the 2004 election in Spain as a 'viral' messaging campaign got out the vote.

US industry figures showed that 158 billion text messages were sent in 2006 between Americans, who own some 243 million mobile phones. About 43 per cent of Americans aged from 18 to 24 text daily, according to Insight Express, as do 10 per cent of the 55- to 64-year-old generation.

'It could be an incredibly useful mobilisation tool,' said Ms Julie Germany, deputy director of the Institute for Politics, Democracy and the Internet at George Washington University.

The use of text messaging 'is catching on a little bit in the US, but it is nowhere near as big as it is in places like Europe, Latin America and Asia'.

Princeton University graduate student Aaron Strauss, who has researched technology and elections, said that savvy candidates are looking to SMS to reach younger voters, whose participation has been disappointing in recent years.

His study showed that people who received a text message reminder ahead of an election were about 4 per cent more likely to vote than those who did not.

'The newest generation of voters is starting to use text messaging and, as they become politically active, I think you'll see text messaging become more important in campaigns,' he said.

Ms Clinton said in a statement on the launch of her service: 'By harnessing the power of text messaging, we can engage voters in the political process using the latest technology and provide personalised, local campaign updates to our supporters nationwide.'

Ms Julie Ask, an analyst at Jupiter Research, said that Mr Obama appeared to have an early edge in using mobile technology, with a snappier code - 62262 spells Obama, for example - and with mobile content and 'wallpaper' for phones.

She said that candidates should not assume that only young voters would be moved by text.

'I would remind (candidates) that the percentage of cellphone users aged 55 and over using text messaging doubled last year,' she said.

But analysts say the US is not ready for the 'smart mobs' created by SMS.

Americans are less frequent text messagers because they use e-mail more frequently and because mobile operators charge 10 cents to 15 cents per message, which can be costly for frequent users.

So far, Republican candidates have yet to use mobile messaging.

AGENCE FRANCE-PRESSE