President Carter is expected to announce this week the appointment of Carol Tucker Foreman, president of the Consumer Federation of America, an assistant secretary of agriculture for consumer services, Agriculture Department sources said yesterday.

Foreman's appointment to the post has been strongly opposed by agriculture interests, who regard her and her organization, the nation's largest such group, as no friend of the farmer.

But under a plan recommended by Agriculture Secretary Bob Bergland to Carter, the responsibilities of the consumer services post would be diminished, with many areas of responsibility transferred to the supervision of an assistant secretary for marketing services.

According to department sources, Robert Meyer, a cattle rancher and cotton grower from Brawley, Calif., will be appointed to the marketing post.

This reorganization represents a compromise on Foreman's appointment, which was strongly opposed by such interests as California fruit and vegetable farmers, Florida citrus growers and milk cooperatives. They did not want Foreman to be in charge of the marketing orders, some of them claiming she would try to destroy them.

Marketing orders are federal regulations that enable farmers to limit the amount of their products brought to market in order to establish or stabilize prices and to standardize quality.

There has been an overall mistrust by farmers of consumer spokespersons like the Arkansas-born Foreman, which was fostered by former Agriculture Secretary Earl Butz. Butz often told farmers that consumers thought farmers were making too much money.

Bergland, who took office Sunday, told a reporter recently that he had been "getting hammered over the head by commodity organizations and old liners" not to appoint the 38-year-old Foreman.

Organizations such as Community Nutrition Institute, which monitors the Agriculture Department's policies, and Ralph Nader's Congress Watch strongly favored the Foreman appointment and have opposed the division of the department into two segments.

Under the plan Bergland has recommended to the President, the 43-year-old Meyer would be in charge of marketing orders and Foreman would oversee federal feeding programs such as food stamps and meat and poultry plant inspection. According to a spokesman in Bergland's office, Foreman and Meyer would then "sit down and divvy up the remaining agencies" that had been in marketing and consumer services before.

But Rod Leonard, director of Community Nutrition Institute, said that taking the marketing orders away from Foreman would make her department a "consumer ghetto" in USDA.

Foreman, however, is willing to accept the truncated department. Both she and Meyer were members of the National Carter Committee for Food and Nutrition.