The European Economic Community tentatively agreed yesterday to limit steel exports to the United States in an effort to avoid duties and settle an eight-month trade rift that has strained ties between the United States and its Western allies.

The European Community's decision must be affirmed this morning by the West German cabinet, however, before it can be sent to Washington for approval by the Reagan administration and U.S. steel manufacturers, who last August rejected an earlier U.S.-EEC agreement.

In this complex, three-stage process necessary to avoid the imposition of duties, the American steel manufacturers have until Thursday to signal their assent by withdrawing complaints against the Europeans they had filed with the U.S. International Trade Commission. The duties were triggered by an ITC ruling Friday that imports from the government-subsidized European steel companies hurt their American competitors.

Steel industry sources here believe that the American manufacturers will go along with the new European concessions.

The European Community, generally known as the Common Market, bowed to American industry demands and included steel pipes and tubes -- used by the oil and chemical industries -- in its quota agreement. These amount to about one-third of the 6.65 million tons of steel Europe shipped to the United States last year. Earlier, the Common Market nations agreed to add alloys to 11 common steel products on which it had approved limits in August.

The August agreement called for cutbacks in the export of European steel to 5.76 percent of the American market until 1985 compared with 6.3 percent last year.

West Germany is concerned because it provides only minimal subsidies to its steel industry, and the ITC ruled in two of four cases Friday that its imports had not harmed the American domestic manufacturers. Germany told its fellow Common Market nations yesterday that its tube and pipe sales were not unfairly priced or subsidized, Reuters reported, and won a concession allowing it to continue imports even if they approached the 5.9 percent cutoff limit.