WASHINGTON – Maine and 12 other states are expected to join California in imposing tougher pollution controls on new heavy-duty diesel trucks and buses sold beginning in 2005, state officials said Monday.

The action is aimed at forcing manufacturers of big diesel truck and bus engines to comply with more-stringent testing procedures for engines sold in each of the states, officials said.

The pollution control requirements would not directly affect trucks already on the road, but likely will increase pressure on manufacturers to build cleaner vehicles. The 13 states account for nearly two-thirds of the new heavy-duty diesel trucks sold, according to state and federal officials.

The federal government already has proposed regulations for new testing standards to begin by 2007, but the state action is aimed at forcing compliance two years earlier, in 2005.

California is expected to formally approve the new requirements next month and other states have indicated they plan to follow with rules of their own, according to officials representing state air pollution control agencies.

The state effort is hoped to “bridge a gap” between requirements reached as part of a 1998 consent agreement between the Justice Department and engine manufacturers and the new federal requirements, said William Becker, whose organizations represent state and local air pollution control officials.

“The manufacturers are even now trying to get out of the consent decree, saying they can’t meet it,” said Becker, executive director of the State and Territorial Air Pollution Program Administrators and Association of Local Air Pollution Control Officials.

The two organizations were to announce the new state actions later Monday.

Under the federal Clean Air Act, states are free to adopt pollution controls more stringent than the federal requirements if they follow the lead of California, which because of its historically dirty air has the authority to draft its own air rules.

Joining in support of the tougher California standards, in addition to Maine, are New York, New Jersey, Massachusetts, Connecticut, Rhode Island, New Hampshire, Vermont, Delaware, Georgia, North Carolina, Texas and Nevada.

The Environmental Protection Agency is writing new exhaust rules for diesels but they won’t take effect before 2007.

Robert W. Perciasepe, who heads EPA’s air-pollution effort, told The New York Times the agency supports the 13 states’ action as a backstop to the federal program.

In 1998, diesel engine manufacturers promised, as part of a consent agreement with the Justice Department, to conduct tougher pollution-testing procedures, beginning with 2002 engine models, to better reflect actual driving conditions when they certify new engines. The new requirements under the consent agreement would be mandatory by 2004.

The manufacturers, who produce most of the heavy-duty diesel engines, also agreed to pay $1 billion in penalties, for past violations.