NEW YORK (Reuters) - Cablevision Systems Corp <CVC.N> said on Thursday it plans to spend $350 million to build a wireless broadband network to serve its subscribers in the New York area.

Chief Operating Officer Tom Rutledge said the new network, which will be completed within the next two years, will be accessible via Wi-Fi-enabled portable devices such as iPhones and laptops.

"Ultimately it will be a mobile voice-capable network," said Rutledge.

He said the network will be accessible for free to existing customers but that as average customer revenues and cash flows rise the company would benefit by offering a more comprehensive service for customers.

"Creating this value proposition for customers will enhance our service and cement our relationship with customers for the long haul," said Rutledge.

"It will allow us to offer our services beyond our network," he added.

Cablevision said it has been testing the service, which will have speeds up to 1.5 megabits per second, comparable to traditional wireless networks, in small areas across its 3.1 million-strong customer base.

Cable companies have been investigating ways to extend their video, Internet access and phone services beyond their traditional cable operations with a wireless strategy in a bid to fight off competition from phone companies' wireless services.

News of Cablevision's wireless plans comes after larger cable companies Comcast Corp <CMCSA.O> and Time Warner Cable Inc <TWC.N> teamed up with wireless companies Sprint Nextel <S.N> and Clearwire Corp <CLWR.O> in a new $14.5 billion wireless venture that will use WiMax technology.

Cablevision shares were up 10 cents at $23.85 on the New York Stock Exchange.

(Reporting by Yinka Adegoke; Editing by Brian Moss)