The nation's business economists expect the U.S. economy to continue to expand in 1988, but at a slower pace than this year, according to a survey by the National Association of Business Economists.

The poll results, released at the association's annual meeting in New Orleans, indicated that business economists expect the gross national product to grow 2.7 percent next year, down from 3.0 percent this year. Last year's survey had projected GNP growth of 2.9 percent for 1987.

The survey also found growing concern about inflation, with those surveyed expecting prices to rise 4.5 percent this year and 4.8 percent in 1988.

"While the nation's business economists have generally maintained their confidence about real growth, they have become more pessimistic about inflation," said Jerry L. Jordan, the association's president.

Most of the economists reported an improvement in business conditions at their firms, the NABE said. Nearly 70 percent said demand for their products was increasing, the highest level since l984, according to the association.

The survey said the economists also forecast:

A small cut in the nation's merchandise trade deficit this year, to $155 billion from $156 billion last year. However, they projected a decrease to $140 billion in 1988.

An increase in real capital spending of 3.4 percent, compared with decreases of 1 percent this year and 2.3 percent in 1986.

Auto sales of 10.5 million, up only slightly from the expected 10.3 million this year and down sharply from 1986's 11.4 million.

A decrease in housing starts to 1.6 million, off from 1.65 million this year, due to rising interest rates.

Jordan said that while that most business economists are pushing back the expected starting date of the next recession, "they still believe that a downturn will occur before the end of 1990."

"High 'real' interest rates, too little new investment in the U.S. economy, and slow long-term productivity growth were mentioned as key forces which could bring about a new economic downturn," he said.

The NABE found its membership divided on how to deal with the dollar's weakness.

Nearly 30 percent supported this spring's tightening of reserve growth by the Fed and intervention in foreign exchange markets to support the dollar, while about 13 percent supported intervention but opposed the tightening of domestic monetary policies.

Nearly a third took the opposite view, supporting the Fed moves but opposing central bank buying, while the remaining one-quarter objected to both actions, the NABE said.