Telecommunications firm AT&T has said it will spend US$565m over ten years to replace or buy about 15,000 vehicles in its corporate fleet, aiming to renew with vehicles that run on alternative fuels.

The company said the investment would be the biggest of its kind by a US company and Ford will be a big beneficiary.

AT&T Chief Executive Randall Stephenson told the Economic Club of Washington that the company will buy about 8,000 Ford-supplied vans or technician trucks that run on compressed natural gas over five years.

"Natural gas is cheaper, cleaner and we have plenty of it here domestically," Stephenson said.

AT&T also plans to replace 7,100 other vehicles with hybrids and other advanced technology power systems over 10 years.

The hybrids will include a combination of gas-electric and plug-ins, and the trial includes mostly those made by Ford, with some from Toyota Motor Corp, according to Tim Harden, president of supply chain at the company.