AT&T (NYSE:T), the largest telecommunications company in the United States announced its $4.85 billion tower agreement with Crown Castle International Corp. (NYSE:CCI) on Monday.

Under the terms of the agreement, AT&T agreed to lease the rights to its approximately 9,100 wireless towers and to sell 600 AT&T towers to Crown Castle. According to AT&T, the average term of the lease rights is 28 years. Crown Castle has the option to purchase the towers at a fixed price of $4.2 billion after the expiration of the leases. The amount was based on the estimated fair market value of the towers by the end of the lease terms.

AT&T will said it will sublease capacity on the towers from Crown Castle for a minimum fee of $1,900 per month per site for a minimum of 10 years. The rate is will increase 2% every year. The company said it has the option to renew the leases up to 50 years.

In addition, AT&T has the access to additional reserve capacity on the towers to use in the future. According to the company, it will be able to continue to meet the growing demand for mobile internet services through additional capacity from the towers. Its agreement with Crown Castle does not have impact on customer experience.

Crown Castle has full operating rights and responsibilities for the towers during the terms of the leases. It has the authority to sublease other available space to other companies.

In a statement, Bill Hogg, senior vice president of Network Planning and Engineering at AT&T Services said, “This deal is good for AT&T and our shareholders. This deal will let us monetize our towers while giving us the ability to add capacity as we need it. And we’ll get additional financial flexibility to continue to invest in our business, maintain a strong balance sheet and return value to our shareholders.”

AT&T CEO, Ben Moreland emphasize that its transaction with Crown Castle is “about growth, pure and simple.” The company is well experienced in this type of transactions given the fact that it owns around 15,000 towers, and majority are being managed by other parties.  The company expects to close the deal by the end of 2013.

The stock price of AT&T gained 1.76% to $35.22 a share on Monday.