President Reagan yesterday called the report of a U.S.-Canadian team on acid rain "an important step forward," but did not say if he will support its recommendation for a five-year, $5 billion effort to encourage clean coal-burning technology.

In a written statement, Reagan said only that the report would get a careful review before he meets with Canadian Prime Minister Brian Mulroney in March.

The 35-page document delivered to Reagan yesterday by special envoy Drew L. Lewis contains little new information about the phenomenon of acid rain, but its conclusions contrast starkly with the administration's previous position that more study is needed on its causes and effects before taking action.

"We can't keep studying this thing to death," Lewis said in an interview yesterday. "We have got to do something about it."

The sentiment won hearty support from environmental groups and their allies in Congress, although most criticized the recommendations of the report that capped an eight-month effort by Lewis and his Canadian counterpart, former Ontario premier William G. Davis.

"It represents a change in administration policy, which is welcome," said Sen. George J. Mitchell (D-Maine), who has sponsored legislation to reduce by 10 million tons the sulfur emissions that are generally accepted as the major cause of acid rain.

Mitchell said the Lewis-Davis proposal would cut emissions by an estimated 2 million tons and was "inadequate to the task" of preventing further acid-rain damage. He also questioned whether there would be funds to support it at a time of general budget-tightening.

As outlined by Lewis and Davis, the federal government would put $2.5 billion into the commercial development of clean-coal technology. The other $2.5 billion would come from industry, largely the midwestern coal-fired power plants that are the heaviest sulfur emitters.

The proposal is carefully crafted to minimize opposition from electric utilities and coal producers, which have bitterly fought past legislative efforts to control acid rain.

The National Coal Association gave the recommendation a cautious endorsement, applauding its "emphasis on clean-coal technology." The association did not retreat an inch, however, from its position that there is no solid evidence linking coal-burning to acid rain.

The Edison Electric Institute, a utility association, was more enthusiastic. "The industry has long believed that investment in clean-coal technology is the most cost-effective approach to addressing the acid-rain concerns of the American and Canadian people," the institute said in a statement.

Susan Roth, an EEI spokesman, said cleaner methods of burning coal have been proved in demonstration projects and "we've been looking for federal funding to bring it into the commercial arena."

Lewis acknowledged that financing the federal half would be a major obstacle. The White House accepted only reluctantly last year a $400 million, three-year program to demonstrate clean-coal technology, and the Office of Management and Budget is not expected to welcome a sixfold increase.

"I understand about Gramm-Rudman and cutting the budget," Lewis said. "It's a matter of priorities."

He said he had offered his services to Reagan as a lobbyist for the proposal "because I think it's right for the country," and had urged the president to assign a high-level Cabinet official to take charge of the acid-rain program.

"We want to make sure this doesn't get buried somewhere," Lewis said.

In Canada, the report was greeted with a mixture of disappointment and derision. Mulroney had no statement on the recommendations, but his political opposition pounced on them.

"I call it a failure," said Bill Blaikie, the environmental critic of the opposition New Democratic Party. "It flies in the face of Canada's longstanding demand that the U.S. act quickly and it puts Canada right back where we were when negotiations started."

Adele Hurley of the Canadian Coalition of Acid Rain, which includes environmentalists, unions and tourist interests, called the recommendations "pretty thin material."

Davis defended the proposals, although he acknowledged that he did not expect them to be "loudly and wildly acclaimed" by Canadians, who had hoped for mandated reductions in sulfur emissions.

In a letter to Mulroney, Davis said the proposal should result "in some near-term reductions in U.S. air emissions," but he said Canada should press for an agreement requiring set reductions.