Home Depot today will introduce a label for nearly 3,000 products, like fluorescent light bulbs that conserve electricity and natural insect killers, that promote energy conservation, sustainable forestry and clean water.

The initiative — which is expected to include 6,000 products by 2009, representing 12 percent of the chain’s sales — would become the largest green labeling program in American retailing and could persuade competitors to speed up their own plans.

And it signals that Home Depot, the country’s second-largest retailer, is joining the largest, Wal-Mart, in pursuing issues of public concern like climate change that stores have left to governments and environmental groups.

More than 90 percent of the products in the line are already on Home Depot’s shelves, but the Eco Options brand will identify them as environmentally friendly.

Home Depot executives said that as the world’s largest buyer of construction material, their company had the power to persuade thousands of suppliers, home builders and consumers to follow its lead on environment sustainability. “Who in the world has a chance to have a bigger impact on this sector than Home Depot?” said Ron Jarvis, vice president for environmental innovation at the retailer, which is based in Atlanta.

But persuading the majority of Americans to buy less polluting products could prove an uphill battle, at least for now, environmental advocates say. Decades of research have shown that consumers often say they want sustainable products but rarely purchase them. Prices tend to be higher, and consumers complain that the products do not always work as well as those they are meant to replace.