Sharing of 3G mobile network infrastructure between operators in the UK does not breach European Union competition rules, the European Commission has ruled.
The commission has also approved national roaming agreements between licensed network operators, as this will "benefit consumers by allowing operators to offer better and quicker coverage", the commission said.
Allowing network sharing and roaming will help launch 3G mobile services.
"This decision strikes the right balance between infrastructure competition in 3G markets and the immediate consumer benefits of having faster and wider rollout of 3G services," said competition commissioner Mario Monti.
The decision will give guidance to mobile operators on how far they can co-operate with each other while remaining within European competition rules, he added.
Roaming between operators will exclude the 10 largest cities in the UK, where operators will each be obliged to build their own networks.
National roaming in smaller cities will be exempt from competition rules until the end of 2007, and rural areas will be exempt until the end of 2008.
Last September the commission approved plans by two of the UK's five 3G operators to share their infrastructure.