The volume of world trade hit an all-time high in 1984, registering a 9 percent increase over the previous year, according to a report from the General Agreement on Tariffs and Trade (GATT).

The gain was the largest in eight years, GATT's economists said in their first assessment of world trade trends, released today. But they warned that the "lopsided" pattern of world economic growth would prevent such a percentage increase being repeated in 1984.

"The impressive growth of output and employment in the United States contrasts with the weak growth and further increase of unemployment in Western Europe," the GATT report said.

"The imbalance in growth rates between Western Europe and the United States is clearly an important source of tension in the world economy. Some convergence of economic growth rates between the two areas is widely expected to develop during 1985, but this development will be, for the most part, the result of lower growth in the United States," the report said.

"On the basis of current indicators, economic expansion in Western Europe, while accelerating somewhat, is anticipated to fall short of the standards achieved in past recoveries, and unemployment will remain high."

The GATT report predicted that the volume of world trade in 1985 would increase by about 5 percent. GATT normally produces two estimates of world trade flows in the preceding year, the first in March, when preliminary figures are available, and the second in the summer when the organization has more detailed information available.

The report said preliminary estimates are that economic growth in industrialized countries such as the United States will continue in 1985 at the same rate as the last half of 1984. But it warned of continued world trade tensions, and said the fact that the economic recovery of Europe had not been as strong as that of the United States gives continuing cause for concern.

It also noted that while the United States is generally undergoing a recovery, some sectors of the American economy are suffering, especially farmers.

In addition, the report said, "a number of basic [U.S.] industries have found, like their counterparts in Western Europe, that the end of the recession did not mean an end to their economic difficulties."

Given the strength of the dollar, the report said, "this suggests a decline of a more fundamental nature in the international competitiveness of these basic industries."

The report said world agricultural output recovered by 3 1/2 percent, after a 7 percent decline in 1983, in developed countries. But Third World and Soviet bloc countries failed to match this growth, it said.