The number of mobile phone users will overtake the number of non-users this year for the first time, according to the UN telecoms agency.
Ownership rates in developing countries are rising fastest, with Brazil, Russia, India and China alone accounting for one billion subscribers last year, the International Telecommunication Union said.
In 2000, only 12 per cent of the global population had a mobile phone.
"At current growth rates, global mobile penetration is expected to reach 50 per cent by early 2008," according to ITU's January newsletter.
This would amount to more than 3.3 billion subscriptions worldwide.
ITU said the figures, gathered from mobile service providers, did not take into account people who have more than one phone and that some operators might inflate their subscriber numbers.
"On the other hand, some subscribers, particularly in developing countries, share their mobile phone with others, thus spreading its benefits," the agency said.