Ericsson has claimed the lion's share of a £2.1bn contract with Cingular Wireless.
It joins forces with Nokia in the project to upgrade the second-largest US phone company's network.
Nokia's share is worth £700mn.
The companies will provide equipment based on the global system for mobile communications standard, or GSM, as well as systems for faster Internet access.
Siemens said it will also supply handsets to Cingular.
Cingular first announced the order in October, without giving details.
It said it was joining forces with VoiceStream and agreed to co-operate in New York, Nevada and California.
At the moment, only about a quarter of Cingular's customers use the GSM standard.