Under the terms of the 3G licences auctioned by the UK government in 2000, licence-holders must be able to reach at least 80 percent of the UK population with their 3G networks by the end of 2007.
3, which was the first operator to launch 3G handhelds in the UK, announced this week that it had already reached this point.
"As we build our network further, more of Britain will be able to experience what is fast-becoming a revolution in telephony," said Bob Fuller, chief executive of 3 UK, in a statement.
"Coverage has been a key part of our strategy since launch and we intend to remain the market leader for 3G coverage."
To reach this target, 3 has installed 6,000 base stations -- up from 1,000 at the start of this year. At present, it had a sizeable lead in coverage over Vodafone and Orange, the two other operators who have launched 3G phones.
Orange says it has reached the 70 percent mark, and is confident of adding at least another 10 percent over the next two years.
"We're aiming to hit 80 percent population coverage by the end of 2006," said Orange spokesman Stuart Jackson.
Vodafone, which launched its 3G handsets a few weeks ago, is claiming 60 percent 3G network coverage today. It also says it will beat the 2007 deadline.
"We're incredibly confident that we will hit 80 percent well in advance of the end of 2007," said a Vodafone spokesman, adding that 3G network coverage was a "very high priority" for the company.
Because the operators started installing their 3G infrastructure in major cities and are now expanding to less densely populated areas, it will take progressively more effort to increase network coverage.
While the 3G phones currently on sale are aimed more at the consumer market than business users, their video calls functionality could be very useful to some enterprises. And because Vodafone and Orange both also sell 3G data cards -- as do T-Mobile and O2, which have yet to launch handsets -- their 3G network coverage is an important issue to many mobile workers.
Orange's 3G handsets went on sale in the UK on Friday. To mark the event, the company supplied all staff with commemorative T-shirts to mark the event. Within hours, one employee had stuck his limited edition T-shirt on eBay.
"This t shirt [sic] commemorates a landmark in advanced communications and will be much sought after item in years to come when we will all be taking 3G for granted," claimed the seller.
However, by Friday afternoon the item had only attracted a top bid of £7.50.