Ou Virak is on a two-week trip to the US, where he met with senior State Department officials and representatives of Congress.
Prime Minister Hun Sen and his Thai counterpart met on the sidelines of a UN-Asean summit in Hanoi on Thursday.
Frieden also called for wider implementation of a World Health Organization policy package.
Clinton will arrive in Cambodia Saturday and stay through Monday.
Ban said he felt the government was “committed to completing the process” of the court and that Cambodians seek and deserve justice.
Soun Sophoan, who attempted to lead 30 activists toward Ban's motorcade, remained in serious condition on Thursday night.
Pung Chiv Kek, founder of the rights group Licadho, said Cambodia must appreciate the meaning of the Paris Peace Agreement of 1991.
Rights groups and other residents have looked for him to address what they say is a deteriorating rights situation in Cambodia.
One in five Americans has irritable bowel syndrome.
Cambodian-Americans face social, cultural and economic difficulties, along with similar communities from Laos and Vietnam.
Decades of conflict shattered Cambodia's infrastructure - its roads, ports and railways.
Residents said in a letter they wanted “to stop the forced eviction from their homes and lands.”