The GATT report, from the secretariat of the 101-nation organization, said growth in world trade and output was likely to slow in 1991 for the third straight year. But it said a global recession was unlikely despite uncertainties in the aftermath of the Persian Gulf war.

The preliminary report, compiled from information available by early March, said worldwide merchandise trade volume rose by 5 percent in 1990, compared with 7 percent in 1989 and 8.5 percent in 1988. Trade value rose 13 percent, to a record $3.5 trillion, largely because of the dollar's weakness.

Trade in services grew an estimated 12 percent, to $770 billion, from $690 billion in 1989, it added. Crisis Contributed to Lag

Economic disruption and uncertainty caused by the gulf crisis contributed to slower economic growth in 1990, the report said, but probably did not play an important role.

Saudi Arabia recorded the biggest jump in export rankings, to 21st place, from 25th, as earnings rose by nearly 40 percent, to $39 billion, because of sharply higher oil exports and prices for crude oil.