Between 1955 and 1963, the United States provided $409.6 million in economic grant aid and $83.7 million in military assistance. This aid was used primarily to repair damage caused by the first Indochina war, to support internal security forces, and for the construction of an all-weather road to the seaport of Sihanoukville, which gave Cambodia its first direct access to the sea and access to the southwestern hinterlands. Relations deteriorated in the early 1960s. Diplomatic relations were broken by Cambodia in May 1965, but were reestablished on July 2, 1969. U.S. relations continued after the establishment of the Khmer Republic until the U.S. mission was evacuated on April 12, 1975. During the 1970-75 war, the United States provided $1.18 billion in military assistance and $503 million in economic assistance. The United States condemned the brutal character of the Khmer Rouge regime between 1975 and 1979. The United States opposed the subsequent military occupation of Cambodia by Vietnam, and supported ASEAN's efforts in the 1980s to achieve a comprehensive political settlement of the problem. This was accomplished on October 23, 1991, when the Paris Conference reconvened to sign a comprehensive settlement.

The U.S. Mission in Phnom Penh opened on November 11, 1991, headed by Charles H. Twining, Jr., who was designated U.S. Special Representative to the SNC. On January 3, 1992, the U.S. embargo was lifted, thus normalizing economic relations with Cambodia. The United States also ended blanket opposition to lending to Cambodia by international financial institutions. When the freely elected Royal Government of Cambodia was formed on September 24, 1993, the United States and the Kingdom of Cambodia immediately established full diplomatic relations. The U.S. Mission was upgraded to the U.S. Embassy, and in May 1994 Mr. Twining became the U.S. Ambassador. After the factional fighting in 1997 and Hun Sen's legal machinations to depose First Prime Minister Ranariddh, the United States suspended bilateral assistance to the Cambodian Government. At the same time, many U.S. citizens and other expatriates were evacuated from Cambodia and, in the subsequent weeks and months, more than 40,000 Cambodian refugees fled to Thailand. The 1997 events also left a long list of uninvestigated human rights abuses, including dozens of extrajudicial killings. Since 1997, U.S. assistance to the Cambodian people has been provided mainly through non-governmental organizations, which flourish in Cambodia.

The United States supports efforts in Cambodia to build democratic institutions, promote human rights, foster economic development, eliminate corruption, achieve the fullest possible accounting for Americans missing from Indochina conflict, and to bring to justice those most responsible for serious violations of international humanitarian law committed under the Khmer Rouge regime.

The U.S. Embassy in Phnom Penh is located at 27 EO Street 240. Tel: (855) 23-216-436, fax: (855) 23-216-811.