UPS, the world's largest shipping carrier, says it has ordered 200 hybrid electric vehicles and another 300 compressed natural gas vehicles as it seeks to make its fleet more fuel efficient and environment-friendly.

The Atlanta-based company, also known as United Parcel Service, did not say how much it is paying for the 500 vehicles.

They will increase UPS' alternative fuel fleet from 1,718 to 2,218 low-carbon vehicles -- more than 2 percent of its worldwide fleet of 93,000.

The 200 hybrid electric vehicles, which will be used starting in 2009, are expected to save 176,000 gallons of fuel annually.

The 300 compressed natural gas vehicles will be used starting later this year.

UPS has its main international air hub in Louisville, Ky.