SAN FRANCISCO, United States — Google Inc. plans to unveil a "buy" button for its advertising service, stepping up pressure on rival Amazon.com Inc. as the Web company moves deeper into online commerce.

The tool, which will let users purchase items from Google’s search results pages, is “imminent,” Chief Business Officer Omid Kordestani said at a Re/code conference in Rancho Palos Verdes, California. The Wall Street Journal reported earlier this month the company would introduce buy buttons, citing people familiar with the matter.

Google is looking for new ways to keep users on its services as it seeks to boost sales. The company is under growing pressure from Amazon and other e-commerce companies as consumers increasingly shop for items on the Web without going through Google’s search service.

By Brad Stone, Brian Womack; editors: Jillian Ward, Reed Stevenson, Andrew Pollack.