WASHINGTON -- At least 3.1 million Americans are employed in green jobs, a sector that accounts for about 2.4 percent of the nation's total employment, the Labor Department said Thursday.

The report is the first official count from the department's Bureau of Labor Statistics of environmentally friendly jobs, a centerpiece of President Obama's stimulus plan.

The report makes no assessment of when the jobs were created and says its figures are from 2010. It found 2.3 million green jobs in the private sector and 860,300 in the public sector.

In the private sector, manufacturing had the greatest number of green jobs, with about 461,800, about 4 percent of all manufacturing employment. Construction was second, with about 372,000 jobs.

Vermont had the highest proportion of green employment at 4.4 percent, while Florida had the lowest at 1.3 percent. California had the largest number of green jobs, with 338,000 workers.

The bureau devised a two-part definition of green jobs in 2010. The first part counts "output-based jobs" that produce goods and services benefiting the environment or conserving natural resources. That includes a company producing solar panels or a farmer growing organic tomatoes.

The second part of the definition covers "process-based jobs" where workers make a company more environmentally friendly or use fewer natural resources. That would include an employee in charge of recycling at a manufacturing plant even if the plant itself is not green.

A nuclear power plant is green because it produces energy without causing harmful greenhouse gases, said Rick Clayton, a bureau spokesman. The report, which was released Thursday, includes only jobs under the first part of the definition.

First Published March 23, 2012, 2:39 a.m.