“There are no examples we know of a regime undertaking wholesale investigations of its own troops or senior officials for war crimes while that regime or government remained in power. In Sri Lanka this is further complicated by the fact that responsibility for many of the alleged crimes rests with the country's senior civilian and military leadership, including President Rajapaksa and his brothers and opposition candidate General Fonseka.”
See the full text of a US Embassy cable of January 2010, released by Wikileaks to The Guardian newspaper here.
The US cable also says Tamil political leaders in Sri Lanka fear for their lives if they demand accountability for war crimes, even though they want this eventually: TNA leader R. Sampanthan is quoted welcoming the international community - and especially the Diaspora's - efforts on the issue.
Also, see related article by The Guardian here.