This is what the United States' Permanent Representative to the United Nations, Susan Rice said in response to the release of the UN Panel of Experts' Report on Sri Lanka:
“The US welcomes [the] public release of the ... report. We appreciate the detailed and extensive work of the panel and believe it makes a valuable contribution to next steps that should be taken in support of justice, accountability, human rights, and reconciliation in Sri Lanka.
“We commend the Secretary General for his decision to release the report publicly.
“The United States has been at the forefront of efforts to support an effective, transparent post-conflict reconciliation process in Sri Lanka that includes accountability for violations by all parties.
“The report highlights the need for an independent and full accounting of the facts in order to ensure that allegations of abuse are addressed and impunity for human rights violations is avoided.
“We strongly support the Secretary General’s call for the Sri Lankan authorities to respond constructively to the report and underscore our belief that accountability and reconciliation are inextricably linked.”
See also India's - in contrast to the US's, guarded - response, and related commentary here.