U.S. and Japanese trade negotiators today reached agreement to partially open up Japan's market for American agricultural products, which has been one of the major stumbling blocks to a new worldwide trade liberalization plan being negotiated in Geneva.

The agreement, reached after protracted negotiations last night and this morning, will permit substantially larger quantities of American beef and citrus fruit to enter Japan in the next four years.

The United States, however, did not win one of its major goals -- an agreement by Japan to eliminate all agricultural import restrictions by a certain date. The two sides merely agreed to discuss lifting of all such limitations again in 1983.

Alan Wolff, deputy U.S. special trade representative, said the agreement represented "substantial progress" and would help the Carter administration to "manage" anti-Japanese protectionist measures in the next Congress.

Wolff and U.S. Ambassador Mike Mansfield had met with Japanese negotiators for 14 hours yesterday and were reportedly at an impasse last night over the American demand that Japan spell out a specific timetable for eliminating all agricultural restrictions.

A compromise was reached this morning and both sides appeared satisfied, although the Americans did not get the specific commitment they had sought.

The chief Japanese negotiator, Ichiro Nakagawa, said the agreement will not cause damage to Japanese farmers. He said the extra quantities of beef and oranges to be imported can be absorbed by growing consumer demand in Japan.

The agreement is regarded as essential by the United States. Special Trade Representative Robert Strauss has said that unless Japanese concessions were obtained on these products it would be difficult to get passed through the next Congress the entire package of "Tokyo round" trade concessions being negotiated in Geneva.

The amount of trade dollars involved is a minor part of the overall U.S. Japan trade balance, which is heavily in Japan's favor. Wolff estimated today that the beef and citrus exports from the United States might amount to only $200 million. But he stressed that the agreement is of considerable "symbolic" value in trade politics because the Japanese had agreed to give in somewhat on products that the government had long protected from foreign imports.

The agreement, Wolff said "is a very major contribution toward getting us through some difficult times" in international trade in the coming months.

The agreement calls for Japanese imports of U.S. oranges to increase from 15,000 tons last year to 82,000 tons in 1983. Orange juice imports will grow ten times and grapefruit juice 20 times. Beef imports would grow by 14,000 tons by 1983, to a total of 30,800 tons.