The Reagan administration has appealed a federal judge's order directing the government within the next nine months to begin controlling smokestack pollution widely blamed for causing acid rain.

The Environmental Protection Agency and the Justice Department said in the appeal filed with the U.S. Court of Appeals for the District of Columbia that the timetable issued by the judge was "seriously inadequate."

District Court Judge Norma Johnson, who issued the ruling in July, last Friday rejected the administration's request for another 3 1/2 years to study acid rain before making states reduce sulfur dioxide emissions, primarily from coal-burning electric power plants in the Midwest.

Chris Rice, an EPA spokesman, said the effect of Tuesday's appeal and subsequent stays to be sought later will be to delay any controls for at least a year beyond the nine months that Johnson allowed.

Ruling in a suit brought by seven northeastern states, Johnson cited letters by former EPA administrator Douglas Costle during the last week of then-President Jimmy Carter's term, concluding that acid rain "is endangering public welfare in Canada and the United States."

Those letters, she ruled, amounted to a formal government determination that -- under international provisions in the Clean Air Act -- committed the United States to begin reducing power plant pollution causing acid rain in Canada.

The letters were written to then-Secretary of State Edmund S. Muskie and Sen. George J. Mitchell (D-Maine).

Though no specific states were named in the judge's order, the suit targeted coal-burning power plants in Ohio, West Virginia, Illinois, Indiana, Kentucky, Michigan and Tennessee as the likely points of origin for the pollution.

New York Attorney General Robert Abrams, who led the court fight against the EPA, called the appeal another effort by the administration to ignore "overwhelming scientific evidence" that the Midwest power plants are causing acid rain in the Northeast and Canada.