The former South Korean ambassador who has become the center of a congressional bribery controversy resigned his government post yesterday, renewing hopes that he might eventually cooperate with investigators.

Kim Dong Jo, a foreign policy adviser to South Korean President Park Chung Hee, said he quit because of the trouble his involvement in the case had caused his country.

He also noted that he could not cooperate with congressional investigators while he was an official of his government. This seemed to imply that as a private citizen now he might be available.

Kim's resignation came a day after a House voted to cut $56 million in food aid to Korea because the Seoul government has refused to allow Kim to answer questions about allegedly making payments to members of congress while he was ambassador to Washington from 1967 to 1973.

Sources familiar with the negotiations on Kim's testimony said yesterday they viewed his resignation as a "necessary first step" to cooperation because of Seoul's constant assertion that diplomats are immune from appearing as witnesses.

But Leon Jaworski, special counsel to the House Committee on Standards of Official Conduct, said in a phone interview yesterday that he wasn't as optimistic about Kim's action.

"I can't throw my head up in the air and start cheering," he said. "I believe he has testimony that would be so startling that his government has arrived at a decision that it would be just too bloody for him to come forward, so they have decided to totally stonewall it."

The former Watergate special prosecutor sounded resigned to completing his investigation without information from Kim. "That would mean we only batted .500 on our key witnesses," he said. "We got Tongsun Park, and he and Ambassador Kim were in competition. They were trying to outdo each other. So it does mean we'd have some loose ends."

Businessman Park was indicted on federal bribery charges, butagreed to cooperate with investigators. He testified that he made more than $750,000 in payments, mostly cash, to members of Congress.

Meanwhile, the House committee ended a third day of closed-door consideration of possible disciplinary cases against members who accepted money from Park. It is to reconvene Tuesday.

Rep. Bruce F. Caputo (R-N.Y.), a maverick member of the committee, criticized both Jaworski's pessimism and his colleagues' will.

"It's all beginning to reek of a cover-up," said the freshman congressman, who missed yesterday's committee session to campaign as the GOP candidate for lieutenant governor of New York.

Caputo said it was "disturbing" that Jaworski didn't view Kim's resignation as a hopeful sign. And he said other committee members were leaning too much on staff summaries of evidence against members, without inspecting actual sworn depositions.

In some instaces, he said, the depositions themselves were incomplete because members' attorney limited questioning.

Without Kim's information, the 18-month House probe seems nearly finished. With it, investigators are known to feel they may have cases against several more sitting members for serious violations. Members who have contended they had no way of knowing Park was a Korean CIA operative; would have no such excuse about diplomat Kim.

There were signs that Kim would resign even before the aid cut-off was voted, sources said. It is not uncommon in Korea for officials to leave office when they have been implicated in some activity decided harmful to the country.

While Kim had been a foreign policy adviser in the presidential Blue House since 1975, he was not considered to rank as high as the White House national security adviser, a State Department official noted yesterday.

And next move leading to Kim's cooperation probably will not occur for a few weeks, sources said. "We have to wait for the dust to settle," one said. "Quite a bit of it was kicked up" with the aid cutoff.