BRUSSELS, OCT. 7 -- Europe and the United States today appeared headed for a clash in negotiations to rewrite the global rules on agricultural trade and subsidies.

Common Market planners countered a U.S. proposal to ban farm subsidies with their plan to reduce subsidies only at a later stage, after negotiating world agricultural market-sharing arrangements as part of the Uruguay round of talks to revise the General Agreement on Tariffs and Trade (GATT).

European officials also warned again that if the U.S. Congress passes protectionist legislation it would "threaten the future" of the GATT talks covering both agriculture and services.

Planners for the European Community would give immediate priority to international marketing accords to reduce surpluses in grains, sugar and milk before agreeing to medium-term negotiations on gradually reducing subsidies.

They cautioned that tariffs might actually have to be raised against imports that currently enjoy advantageous terms, such as major U.S. shipments of soybean products or corn glutten feed.

The opening negotiating stance introduced today still must be ratified by foreign ministers of the 12 EC member states.

EC Commissioners Frans Andriessen and Willy de Clercq said they hoped EC ministers would accept their plan at a meeting later this month.

They noted that the U.S. proposal to end subsidies was presented in July and a Japanese position was expected soon. Discussions of the issue would open the substantive phase of the farm portion of the new round of world trade talks launched in Punta del Este, Uruguay, in September 1986.

Leaders of the industrialized nations also discussed broad principles at the Venice economic summit and at the Organization for Economic Cooperation and Development (OECD) in Paris.

The EC negotiators also said they will insist that the agriculture, services and industrial products segments of the Uruguay round be "coupled."

"The Uruguay round goes far beyond agriculture and we will insist on the globality of the negotiations," de Clercq noted. "The timetable also depends on others. We don't intend to slow down the talks, but we don't want to separate issues."

Andriessen again branded the U.S. proposal to ban subsidies as "unrealistic." He added that during a recent visit to Washington "I didn't find anybody who felt it was realistic." He noted that even U.S. farm subsidies amounted to $25 billion to $30 billion a year.

European and American officials have been concerned recently that their trade and economic relations have been increasingly strained. Traditional agricultural and trade squabbles have been burdened by feuds over problems such as Airbus airliner subsidies and European health rules forbidding the use of hormones in imported meat.