State Department spokeswoman Victoria Nuland says the U.S. continues to support Cambodia's U.N.-backed tribunal to bring to justice those responsible for atrocities.
She called for an "expeditious" and "comprehensive" process.
The 87-year-old Ieng Sary, who died Thursday, was one of the three Khmer Rouge leaders on trial in the Cambodia-based court, which opened in 2006. Despite $150 million in funding, there's been only one conviction.
Remaining on trial are ex-head of state Khieu Samphan, who is 81, and former chief ideologist, Nuon Chea, who is 86. Both are frail and have suffered strokes.