The White House yesterday tossed cold water on reports that the administration is prepared to support an acid-rain control program, saying that neither President Reagan nor his chief of staff, Donald T. Regan, has approved such a plan.

The reports stemmed from a meeting last week between northeastern governors and former transportation secretary Drew Lewis, who is serving as a special negotiator on acid rain. Lewis and former Ontario premier William G. Davis are expected to issue a joint recommendation to their respective governments by the end of the year.

Lewis was quoted over the weekend as saying he had White House support for a "modest" program to cut sulfur-dioxide emissions by about 3 million tons a year, at an estimated cost of $1 billion.

White House press aides said yesterday that Lewis had not discussed his findings with the president or Regan, and that the White House had not endorsed any specific plan to control acid rain.

Spokesman Rusty Brashear said he could not comment on what Lewis may or may not have told the governors, but said the White House would not make any decisions on acid rain until it had seen Lewis' formal report.

"It has never been the White House position that we will do nothing on acid rain, only that we must study before deciding what to do," Brashear said.

A spokesman for Lewis said that the negotiators were still some months away from a final recommendation, and that Lewis had intended only to emphasize the administration's support for the negotiating process.

According to sources familiar with the negotiations, Lewis is committed to a control program that shows "a clear reduction" in sulfur emissions. He told the governors last week that reductions of 10 million or more tons, as called for in some legislative proposals, were "unrealistic."

The program is likely to rely in large part on cleaner coal-burning technologies than are now in commercial use, and the overall cost of the recommendation is likely to be in the neighborhood of $1 billion, the sources said.

Sulfur reductions would likely be in the range of 1 million to 3 million tons, but "we're still working on the numbers of what $1 billion gets you," one source said.

Sulfur emissions, chiefly from coal-fired boilers, are believed to be the main precursor to acid rain. According to prevailing scientific theory, the emissions undergo chemical changes in the atmosphere and fall to Earth as acidic snow and rain, damaging lakes, streams and forests and killing aquatic life.

More than 24 million tons of sulfur emissions are lofted into the atmosphere each year in the United States.

Two years ago, William D. Ruckelshaus, then the head of the Environmental Protection Agency, advanced a control program for acid rain that would have cut sulfur emissions by 3 million to 4 million tons in targeted states.

Ruckelshaus, who came into office with an order from Reagan to "tackle acid rain," failed to win White House approval for the program.

For the last five years, the administration has opposed all control programs for acid rain, arguing that not enough is known about the problem to warrant expensive new antipollution rules. Instead, Reagan has supported increased funding for acid-rain research, although aides say he remains privately skeptical that acid rain is caused mostly by man-made pollutants.

The administration's position has become an increasing irritant between the United States and Canada, which contends that much of the damage being done to its eastern lakes is the result of U.S. emissions.

Lewis was named special negotiator on the issue last March, during a summit meeting between Reagan and Canadian Prime Minister Brian Mulroney. The announcement of a new joint effort on acid rain was widely viewed as a graceful way out of a politically sensitive spot for the two executives. The joint negotiations permitted Reagan to stick to his more-research position while providing an achievement for Mulroney, who had campaigned on a strong acid-rain cleanup effort