Facebook testing a "Buy" button

Facebook is testing a "Buy" button in its latest effort to help businesses boost their sales through the world's biggest online social network.

The company said in a statement Thursday that the button will let people buy products directly from businesses without leaving Facebook. A "Buy" button appears at the bottom of sponsored ads and is being tested by a limited group of several small- and medium-sized U.S. businesses.

The move comes as Facebook continues to grow its advertising business. The company will account for 7.8 percent of global digital ad spending this year, up from 5.8 percent in 2013, according to eMarketer. Google, the world's No. 1 recipient of ad dollars, is expected to account for 31.5 percent of ad spending in 2014.

EMarketer analyst Debra Aho said that not long ago, most businesses thought Facebook was better suited for building awareness than driving sales, but the Menlo Park, California-based company is trying hard to change that image.

"With this step, Facebook is becoming even more firmly established as a major player in direct response advertising, and though this test is still only a test, it's a definite sign that Facebook wants to restart its efforts to become an e-commerce company as well," she said.

Facebook says it won't share users' credit and debit card information with other advertisers. The company said it will provide more details once it has gathered feedback from the test.

In January, Facebook said in a blog posting that it was working on offering more ways for direct-response marketers to communicate with Facebook users.

Mobile advertising is one of Facebook's fastest-growing revenue categories. Nearly 80 percent of its users access the site on smartphones and other portable gadgets. In the January-March quarter, earnings nearly tripled and revenue grew sharply as advertising revenue rose 82 percent.

Meanwhile, mobile commerce is growing at a fast clip, and is expected to total $304.1 billion in 2014, up 15.5 percent from the prior year, according to eMarketer. Mobile commerce will account for 19 percent of all e-commerce sales this year, or $57.79 billion.

Facebook shares fell $1.25 to close at $66.41 on Thursday.