The selection of the two suppliers will enable field trials this year and commercial deployment of the LTE (Long Term Evolution), or 4G, technology in 2011, AT&T said in a statement.
"Our ability to work together to meet the demands of a rapidly changing market has been a crucial element in gaining AT&T's continued confidence," said Ericsson CEO Hans Vestberg in a statement.
"We will work just as hard to secure a smooth rollout of LTE and support AT&T in introducing new consumer and business services moving forward."
The popularity of 3G networks, which allow owners of smartphones like Apple's iPhone to surf the internet from anywhere, has caused disruption in communications due to the ever-increasing traffic, analysts say.
LTE technology offers a higher broadband that can be as much as four times faster than 3G or 3G+ networks.
AT&T, which counts 85.1 million mobile phone clients, said its mobile broadband traffic "has grown more than 5,000 percent over the past three years."
The US telecommunications giant announced last month that it would invest $2 billion (€1.45 billion) more this year than in 2009 to improve its 3G networks and prepare the deployment of LTE.
AT&T did not disclose details of its contract with Ericsson of Sweden and US-French company Alcatel-Lucent.
The United States and Scandinavian countries are among the leaders in LTE technology.
Nordic telecom operator TeliaSonera in December announced the launch in Stockholm and Oslo of the world's first commercial 4G mobile network.