SINGAPORE— China, the United States, Singapore, Malaysia and Thailand spent more than $1.3 billion in a largely secret program in the 1980s to support Khmer Rouge and non-Communist guerrillas in Cambodia fighting Vietnamese troops and allied Cambodian forces, the Singaporean senior minister, Lee Kuan Yew, has disclosed in his memoirs.

The program was opposed by the U.S. Congress because lawmakers objected to moves to aid the Khmer Rouge. The Khmer Rouge was driven from Phnom Penh by a Vietnamese-led invasion in January 1979 after a reign of terror and forced labor that lasted nearly four years and killed more than 1 million people.

The administration of President Ronald Reagan was persuaded to support the ultimately successful effort to get Vietnam to withdraw from Cambodia in September 1989 so that elections under United Nations supervision could be held for a new government. The elections were held in 1993 but were boycotted by the Khmer Rouge.

American, Singaporean, Malaysian and Thai officials held regular meetings in Bangkok to coordinate the Cambodian aid program, Mr. Lee wrote in his book, "From Third World to First: The Singapore Story 1965-2000," which went on sale Sept. 16.