The federal Environmental Protection Agency plans to propose new air quality standards for soot by Thursday and issue final standards by Dec. 14 under a tentative agreement with 11 states that sued the agency earlier this year.

The states, including New York and California, blame fine particulate matter from diesel trucks, buses, power plants and other sources for respiratory illnesses and other public health problems. After the E.P.A. postponed tightening soot standards last fall, deferring a periodic update mandated by the Clean Air Act, the states sued in February in United States District Court in Manhattan.

Judge Robert L. Wilkins issued an order on June 2 giving the agency until June 7 to propose new rules but did not impose a deadline for finalizing the standards.