The Lankan military has denied US accusations levelled through photographs during Rapp's visit which came ahead of the March sessions of the UN Human Rights Council.
The US has told Lanka that it could introduce a third successive resolution over rights accountability and reconciliation with the Tamil minority at the Council.
Two previous resolutions both US moved were supported by India.
Rapp's visit met with a protest opposite the US embassy.
A nationalist group slammed the US for interfering in the country's internal affairs.
A protest was sparked when Rapp told the main Tamil party TNA that the March resolution would push for a international war crimes investigation.
