Michael B. Smith, a top U.S. international trade representative during the Carter and Reagan presidencies who helped reduce obstacles to imports and exports on world markets with a blunt and aggressive style at negotiating tables from Asia to Europe, died Nov. 8 at a hospital in Aldie, Va. He was 85.

The cause was pneumonia, said his wife, Deborah Wince-Smith.

“He has been one of America’s strongest advocates, helping to break down trade barriers around the world,” said U.S. Trade Representative Clayton Yeutter when Mr. Smith retired from government service as deputy U.S. Trade Representative to start his own international trade consulting business in 1988.

A Foreign Service officer who was seconded to the trade representative’s office for much of his career, Mr. Smith did not hesitate to threaten retaliatory tariffs, extra duties or other measures against the exchange of foreign goods or services when he felt American products were not getting a fair shake in the world marketplace. He extracted concessions from Japan regarding American semiconductors, from South Korea in letting American insurance companies compete for business, and the European Community on U.S. agricultural products.

The New York Times described him in 1986 as an “ox-like man who sometimes speaks in machinegun-like cadences and sometimes with the thunder of a howitzer” and who hung a sign on his office door that read, “ ‘This is not Burger King. You either get it my way, or you don’t get it at all.’ ''

One trade expert consultant told the paper that Mr. Smith seemed to excel at playing the bad cop to allow his bosses, including Robert S. Strauss and Yeutter, to play nice. “'This is all part of the rhythm of American trade negotiations,” Robert D. Hormats, then-vice president of investment bank Goldman Sachs, observed at the time. “There’s one guy who breaks the eggs, and another who makes a tasty omelet.''

“There’s no question I’m thought of as the tough guy on the block,” Mr. Smith admitted to the Times. ''It doesn’t bother me. It brings an element of realism. They know where I stand. They know where I’m coming from. I don’t think you’ll ever find anyone saying they’ve been misled by me.”

He was “blunt ... as tough as nails,” said Susan Schwab, a former U.S. Trade Representative who had served on Mr. Smith’s staff. He often shunned the verbal niceties of the Foreign Service diplomatic dialogue for a more “colorful language” of street communications, she said.

A family death announcement quoted Mr. Smith as telling “colleagues that if both parties were not fully happy with an agreement, that showed the pact was good and fair because both sides had had ‘to put real skin in the game to reach the finish line.’ ”

Michael Brackett Smith, whose father ran a construction business, was born in Marblehead, Mass., on June 16, 1936. He learned to sail as a child, continuing a tradition of seafaring and Naval service his family traced to 1640. As an adult, he sailed on the Chesapeake Bay in his 34-foot sloop, “Wind,” sometimes with a foreign guest on board with whom he talked trade business.

He used nautical metaphors to illustrate issues he faced as a trade negotiator. A difficult problem was “sailing into the wind.”

He graduated from Harvard in 1958 but his initial application for the Foreign Service was rejected. As a boy he had his spleen removed for medical reasons that, ironically, made him medically unqualified, the State Department said.

His mother was outraged. She protested in a letter to Secretary of State Christian A. Herter. Her son, she said, “played football at Harvard, was on the Harvard swimming and lacrosse teams. ... What’s the matter with you people?”

A day later, the State Department accepted him. He began his career as third secretary at the U.S. Embassy in Iran, and subsequently held junior posts in Chad and France. By the mid-1970s, he was spending most of his time on trade issues — negotiating limits on cheap textile exports from developing countries and the facilitating of U.S. exports of semiconductors, automobiles, aircraft and motorcycles.

He was among the leaders in the 1979 Tokyo Round of multilateral trade negotiations that cut tariffs and slowed the growth of other trade barriers on a range of goods in 102 countries.

After leaving government service in 1988, he formed Rockmere Associates, a consultancy he ran until he was in his late 70s.

His first marriage, to Nancy Hodgson, ended in divorce. In addition to his wife of 33 years, of McLean, Va., and Marblehead, survivors include two children from his first marriage, Eric Smith of Overland Park, Kan., and Leslie Rosen of Nahant, Mass.; two sons from his second marriage, Devereux Smith of Pearl Harbor, Hawaii, and Christian Smith of Washington; eight grandchildren; and three great-grandchildren.