AS VEGAS (Reuters) - Yahoo Inc. on Tuesday said it is launching a service in the United States that lets people make phone calls through the company's instant messaging software. Available in several other countries since December, the service allows people to make calls from their computers for 2 cents a minute or less to the top 30 national phone markets, including the United States. The "Phone Out" service also allows calls from computers to regular phones at varying rates to a total of 180 countries. Using instant messaging for phone calls is one of the latest ways that technology companies are finding cheaper ways to allow people to talk all over the world without relying on traditional phone networks. "Right now the competition is just about cheap voice calls," Forrester Research analyst Maribel Lopez said. The move also attempts to undercut rates offered by Skype, a similar service offered by eBay Inc.. Yahoo Messenger with Voice rates average between 20 percent and 30 percent lower than Skype to many major markets outside the United States, according to a comparison furnished by Yahoo. Tests in the initial five countries where the service launched proved more successful than anticipated, especially in France, said Yahoo Vice President of Communications Brad Garlinghouse, where strong demand for both Yahoo Phone In and Phone Out services occurred. Phone In allows customers to receive calls on their computers from regular and mobile phones for $2.99 a month, or $29.90 a year. Yahoo's service is one among a growing list of competitors, including Time Warner Inc.'s America Online as well as Microsoft Corp.. While initially the focus is on offering cheap phone calling for computer users, the battleground should quickly shift onto mobile and cordless phones, analysts said.