Oct 28 (Reuters) - SBA Communications raised its annual forecast for adjusted funds from operations on Monday, anticipating a steady wireless carrier activity on the back of growing demand for 5G network.

The Boca Raton, Florida-based company also said it would buy more than 7,000 communication sites in Central America from telecom firm Millicom International Cellular S.A. < > for about $975 million in cash.

The company said the acquired sites are expected to generate about $129 million of revenue and $89 million of tower cash flow during their first full year of operations after closing, which is expected in 2025.

The companies have also agreed to a seven-year exclusivity period, during which SBA will have the exclusive right to build up to 2,500 new sites for the telecom firm.

The wireless tower operator is expected to benefit from a surge in demand from U.S. carriers, as they are upgrading their networks to 5G and increasing capacity to meet booming data demand.

The company leases tower space to major wireless carriers including AT&T , T-Mobile US and Verizon Communications .

SBA raised its forecast range for annual adjusted funds from operations to between $13.20 and $13.45 per share, from $13.06 to $13.43.

It now expects annual revenue to be between $2.66 billion and $2.68 billion, compared with its prior expectation of between $2.64 billion and $2.67 billion.

SBA's third-quarter revenue came in at $667.6 million, missing analysts' estimates of $669.8 million, according to data compiled by LSEG.

Adjusted funds from operations - a key measure of cash flow - were $3.32 per share, slightly beating analysts' estimates of $3.30.

The company's site leasing revenue for the quarter ended Sept. 30 fell 1.8% to $625.7 million, while its site development revenue decreased 7.1% to $41.9 million.

(Reporting by Jaspreet Singh in Bengaluru; Editing by Maju Samuel)

((Jaspreet.Singh@thomsonreuters.com; ))