It took just a few weeks as the Environmental Protection Agency's top clean air enforcer for Bill Rosenberg to enjoy the perquisites of power.

Meeting in early 1989 with oil industry lobbyists fighting alternative fuel proposals in the clean air bill, Rosenberg spotted his old sparring partner -- Amoco Oil executive Jerry Levine -- whom he used to debate on the virtues of ethanol. Rosenberg was in private business then and traveled around the Midwest as a hobby, touting the grain-based alcohol as a substitute for gasoline.

Once criticized by Levine for "dabbling" in an unfamiliar area, Rosenberg came face to face with his old adversary for the first time as the EPA's assistant administrator for air.

"I want to thank you for one thing," Rosenberg said. "You convinced me not to dabble in this issue anymore."

The story speaks volumes about Rosenberg, who has emerged in less than two years as the most influential and controversial assistant administrator in the EPA's history. Not only has he mastered the minutia of clean air issues, Rosenberg also understands how to use the symbols and instruments of power to advance his causes, a skill that often has put him at loggerheads with congressional warlords and White House officials.

His turning-of-the-tables on Levine reflected a will to win that was so demonstrable during the recent revamping of air pollution laws that he was dubbed the "pit bull of clean air."

"Bill Rosenberg is about the most dogged and effective advocate I've ever worked with," said his boss, EPA Administrator William K. Reilly. "He has the rare quality of being both very sensitive to policy and having an adept eye for political concerns and opportunities. He thinks in just the kind of way you want a top legislative advocate to think."

It seemed like an odd match at first: Reilly, the patrician-looking, career conservationist known for his powers of conciliation, and Rosenberg, the fast-talking native of the Bronx who made millions of dollars as a real estate investor.

While Reilly was a surprise choice to head the EPA, Rosenberg took a more traditional route to Washington. Active in moderate Republican circles in his adopted home of Michigan and an old friend of Republican pollster Robert M. Teeter, he was invited in March 1987 to have breakfast with then-Vice President Bush and discuss his passion for ethanol, a motor fuel that Rosenberg pitched as a way to cut oil imports, clean the air and enrich grain farmers.

The idea seemed like a natural for Bush's primary campaign in the Midwest, and Rosenberg was asked to contribute to speeches promising to foster ethanol and other alternative fuels in a Bush administration. After the election, he was asked to deliver the campaign pledge at the EPA.

In office, he has served as a foil to Reilly, battling more conservative administration officials on clean air issues so that the administrator "didn't have to get his skirt dirty," according to an EPA staffer.

The clean air bill became the Holy Grail for Rosenberg, an objective he considered vital to stake Bush's claim as environmental president and to protect public health. He is credited with writing the two most sweeping provisions of the administration bill: alternative fuels and the cap on acid rain emissions.

Only after the bill was proposed did the real fight begin for Rosenberg, a war of two fronts. Not only did he lobby Congress, but he also had to shore up administration resolve to support its most far-reaching initiatives.

"He got shot at from all sides on the Hill and from people in the administration who thought he pushed the administration too far from its constituent base," an official said.

In this crossfire, Rosenberg became an obsessive strategist, balancing demands of environmentalists against the realities of a cost-conscious White House and lining up congressional allies to help in disputes with the White House. He was ecumenical in building political coalitions, turning here to presidential counsel C. Boyden Gray for support on alternative fuels, there to the Council of Economic Advisers to endorse the acid rain cap as vital to the bill's free market features.

With flashes of the business entrepreneur he once was, Rosenberg was in perpetual search of clean air deals -- "a first-class spinner," in the words of Bob Grady, the Office of Management and Budget's top environmental official. In meeting after meeting, call after call, he looked for the sweet spot of compromise: what it would take fix a problem.

Last March's negotiations with Senate leaders were at the breaking point when the White House rejected as too costly the Senate's demand for a second round of auto pollution cuts. Enter Rosenberg, who suggested that the cuts be conditional, required only if a certain number of cities exceeded smog limits. The compromise worked, appeasing the Senate and the White House, happy there were no fixed costs.

The wheeler-dealer in Rosenberg won him respect from his staff and some environmentalists, pleased to have a politically savvy bureaucrat working with them. "He helped get a proposal out of the administration that was pretty damn strong when compared to our expectations," said David Hawkins, who held the same job during the Carter presidency and now works for the Natural Resources Defense Council.

"His political antenna is always out," Hawkins said.

But the supersalesman trait so popular with friends inspires distrust in others. Chief among his detractors is Rep. John D. Dingell (D-Mich.), chairman of the Energy and Commerce Committee, who banished Rosenberg from the House in the fall of 1989. Dingell, trying to water down the administration's proposal on alternative fuels, was pushing an amendment that White House Chief of Staff John H. Sununu endorsed in a telephone call to Republican members of the panel.

Reilly, informed of the Sununu concession, telephoned Democratic members from Chicago and expressed opposition to the amendment, embarrassing Sununu and Dingell.

According to congressional sources, Dingell suspected Rosenberg of tipping off Reilly. "Dingell doesn't suffer fools," a House staffer said. "He's not going to waste his time on someone who's not going to come through on a commitment."

Rosenberg's independence infuriated White House officials last month when he refused to endorse new statistics on acid rain in a letter to congressional conferees that could have been used to justify more pollution by utilities.

Bush's domestic policy adviser, Roger Porter, had promised Republican House members to deliver the endorsement on EPA stationery. But when he tried to call Rosenberg and Reilly to send it on the last weekend of negotiations, both men had left town and did not leave telephone numbers where they could be reached.

"When I get focused, first things are first, second things are not at all," Rosenberg said in describing his general operating style.