The deal will add about 15,700 towers in the United States and Costa Rica to American Tower's existing portfolio of 56,000 towers worldwide.
Tower companies are in a scramble to beef up their assets across the world as an explosive growth in data traffic is pushing carriers to spend heavily on upgrading their networks.
Major U.S. telecom companies such as AT&T and Verizon Communications have increased their spending budgets for the current year.
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Global Tower, formed in 2003 by acquiring 187 towers from American Tower, is controlled by a consortium of funds managed by the Macquarie Group.
The latest deal comes a month after American Tower sad it would acquire about 4,500 telecom towers in Brazil and Mexico from Latin American telecom service provider NII Holdings Inc for $811 million.
The deal is expected to immediately add to the company's adjusted funds from operations and is expected to close in the fourth quarter of 2013.
American Tower was advised by Goldman Sachs & Co and EA Markets Securities, while Global Tower's adviser was Deutsche Bank Securities.