President Carter yesterday abandoned for the rest of his term of office one of his most controversial international initiatives - withdrawal of U.S. ground troops from South Korea.

A White House announcement read by presidential assistant Zbigniew Brzezinsi said additional large-scale withdrawals were being postponed at least until 1981, when the situation will be reassessed.

The principal reason given for the change was the recent increase in the U.S. intelligence estimate of North Korean ground forces. The White House statement said that new reductions in American combat elements "should await credible indications that a satisfactory military balance has been restored and a reduction in tension is under way."

Carter formulated his plan to withdraw U.S. forces as long ago as January 1975, when he was a long-shot candidate for the presidency, and he stuck to his idea with determination after taking office. With little support from anyone else and against strong misgivings of South Korea, Japan the U.S. military and powerful elements in Congress, Carter ordered the phased withdrawal in the spring of 1977 and strongly defended it against attack.

Carter fired Maj. Gen. John K. Singlaub as chief of staff of U.S. forces in Korea for saying that the planned pullout would lead to war. But as opposition continued, Carter shifted the timing so that the scheduled withdrawals started slowly, then postponed timing so that the scheduled withdrawals started slowly, then postponed the departure of most of the first group scheduled to leave. In February of this year he placed further withdrawals "in abeyance" to study the new intelligence.

The authorized U.S. troop strength in Korea for been reduced during Carter's presidency from about 41,000 to about 38,000. But most of this was due to the departure of missile and support units whose withdrawal had been planned previously.

The only combat force withdrawn as a result of Carter's decision was an infantry battalion of 674 men. This was more than offset by the arrival of 12 more U.S. Air Force F4 fighter-bombers with 900 men, justified as a demonstration of continued U.S. commitment to South Korea.

In other measures justified partly

In other measures justified partly United States increased the number and visibility of joint exercises with South Korea, increased support for Korean defense industries and created a combined forces command. All these will continue, officials said yesterday.

A compensation package of $800 million, voted by Congress after extensive debate, will be withheld for the most part until withdrawals actually take place.

Some 1,00 to 1,500 troops of a Hawk missile air defense unit are still schedule to be withdrawn next year, in an arrangement set in motion during theFord administration,

The new U.S. intelligence estimate, which represents a higher assessment of long-term activities rather than any sudden jump in actual North Korean forces, increased the communists army aout 25 percent, to more than 600,000 men. Once the new estimate was leaked in January, official defense of the withdrawal plan became increasingly difficult. Based on the new data the Joint Chiefs of Staff officially recommended that the pullout be stopped until 1981.

During Carter's journey to Seoul last month, the South Korean government agreed to a joint proposal for diplomatic talks with North Korea. Carter's hints at the time that he was ready to put aside the troop withdrawal apparently contributed to Seoul's willingness to agree.

North Korea has rejected the plain for three-way talks, at least for now. The White House stattement yesterday suggested a tie between diplomatic progress and future U.S. withdrawals. Critics had argued from the beginning that Carter should not have given up this leverage, such as it is, in announcing hispullout plan. CAPTION: Picture, Carter aide Brzezinski: Reductions "should await credible indication that a military balance has been restored."