Army Chief of Staff Bernard W. Rogers testified yesterday that the Joint Chiefs of Staff recommended a much smaller withdrawal of U.S. forces from South Korea than that eventually ordered by President Carter. The testimony opened a gap for the first time in public between the uniformed service chiefs and Carter's plan.

Joint Chiefs of Staff Chairman George Brown, who is scheduled to testify before the House Armed Service Committee today, has supported Carter's decision to withdraw all U.S. ground troops from South Korea over five years as involving an "acceptable " risk. But Brown did not disclose in previous public appearance that the military had proposed a quite different plan.

Gen. Rogers told the committee yesterday that the joint chiefs recommended " a phased partial reduction" of 7,000 Army troops over the next five years rather than the full withdrawal of ground combat forces that Carter advocated during his campaign for office and which eventually was ordered. Exact numbers have not been announced, but about 33,000 U.S. troops are potentially involved in the Carter pullout.

Defense Department sources said the military recommendation was sent to Secretary of Defense Harold Brown March 7 in a memorandum signed by the staff of the joint chiefs. Such papers carry somewhat lesser weight than papers signed by the uniformed chiefs themselves.

The JCS memo reportedly said it would be militarily imprudent to withdraw all U.S. ground forces before South Korean materiel, military capability and confidence are sufficient to withstand an attack from the North.

Carter's decision, issued in a May 5 White House order, calls for major U.S. aid to be given the Seoul regime to compensate for the removal of American ground troops. The aid program appears to be a critical factor in the joint chiefs' recent position that the full pullout is an "acceptable" risk.

Rep. Samuel S. Stratton (D.N.Y.) who chaired yesterday's hearing, said Rogers' testimony "confirmed some of the fears of those opposing the withdrawal." Stratton proposed that Carter commit the executive branch to reappraise the Korean situation before making a decision to withdraw the last of the three U.S. combat battalions sometime after 1980.

Stratton suggested that such a commitment from Carter would be a compromise which would reassure uneasy lawmakers as well as the uniformed military.

The committee is conducting hearings on the withdrawal plan because of U.S. forces in Korea after telling a ments of Maj. Gen. John K. Singlaub, who was removed as chief of staff of U.S. forces in Korea after telling a reporter that the Carter program will lead to war.

The committee reported yesterday that the White House has rejected its request for a copy of Presidential Review Memorandum 13, the study leading to Carter's decision, and Presidential Directive 12, the withdrawal order.

A letter from a National Security Council official said "their sensitivity, currency and the fact that they are internal decision-making documents of the executive branch" were the reasons for refusal.

No figure has been given for the proposed U.S. aid program for South Korea. Secretary of Defense Harold Brown is scheduled to discuss the question on a visit to Seoul on July 25.

Pentagon sources said at least "hundreds of millions of dollars" would be involved in the U.S. aid plan. Stratton said his impression was that the plan might be "in the billions." Any large scale aid for the repressive Seoul government is likely to be contested in Congress, however.