PORTLAND – The nation’s top environmental official on Tuesday said Maine is a national model in its efforts to reduce diesel school-bus emissions.

Mike Leavitt, administrator of the Environmental Protection Agency, told a gathering outside the Presumpscot Elementary School that Maine is one of only 17 places nationwide chosen for the Clean School Bus USA program.

The program calls for buses to be retrofitted with pollution control equipment to curb emissions. Twenty-six school districts in Maine are participating in the statewide program, the first of its kind in the country, according to the EPA.

“The black puff of diesel smoke will be a thing of the past,” Leavitt said while standing in front of a school bus, addressing a group of third- and fourth-graders, school transportation officials and others.

Maine and Medford, Mass., are the only two places in New England participating in the bus program. Maine received a $567,000 grant from the EPA.

The Maine Department of Environmental Protection is using the money to help school districts across the state buy diesel oxidation catalysts for 300 school buses. The catalysts are supposed to reduce pollution by at least 20 percent.

Maine also has committed to buy 180 new school buses that already are equipped with the catalysts.

Leavitt said the program, which began last year, aims to have all school buses in the country equipped with the catalysts by 2010.

Environmental groups used Leavitt’s visit to protest actions by the Bush administration they say weaken air pollution standards.

The administration has proposed rules that critics say would allow industrial plants to the west and south of Maine to drop more mercury and ozone pollution on the state than is allowed under the Clean Air Act.

Maine’s congressional delegation, along with the state, also has gone on record objecting to the proposed rules.

Brownie Carson, executive director of the Natural Resources Council of Maine, said clean school buses are a good thing, but the EPA needs to commit to pollution reductions at power plants downwind from Maine.

Carson, along with representatives from the National Environmental Trust, the Maine Sierra Club and Environment Maine, met with Leavitt in Portland later in the day to voice their concerns about power plant pollution.

“I think clean school buses are great, but pollution from 1,100 power plants that is dumped on Maine – that has to be stopped,” Carson said. “That’s the real business we have to get at.”