George C. Warner III, a senior official with the U.S. Agency for International Development, pleaded guilty in U.S. District Court here yesterday to illegally accepting more than $10,000 in connection with his responsibility for seed rice contracts for the Cambodian refugee relief program.

Judge Charles R. Richey sentenced him to pay a $10,000 fine within six months and an additional fine of $30,000 to satisfy civil claims brought by the government in connection with Warner's handling of the contracts.

Richey also placed Warner on five years' probation, and suspended execution of a two-year prison term. The Justice Department, which reached a plea agreement with Warner, had suggested that Warner be placed on probation. Warner also agreed to resign as a Food for Peace officer with AID.

Brendan V. Sullivan Jr., an attorney for Warner, told Richey yesterday that during his 15-year career, Warner had pursued his efforts to supply food for needy people throughout the world with a "missionary's zeal."

Warner, who appeared to be holding back tears, told Richey: "I have made a mistake and I'm sorry for it."

Warner was arrested last September in a Georgetown hotel room by FBI agents and Justice Department officials after he allegedly accepted money from a shipping firm headquartered in Bangkok. The meeting was videotaped by law enforcement officials.

As a result of the plea agreement, the government dropped a three-count indictment against Warner that charged him with bribery, conspiracy and interference with commerce through extortion in connection with his handling of a contract for rice for Cambodian refugees. Warner pleaded guilty to a single, lesser charge of illegally accepting a gratuity while he was a public official.

Richey said that Warner, who is expected to live in South America, will be allowed unrestricted travel after the fines are paid.