GENEVA (Reuters) - The United Nations will release a major report on Wednesday on war crimes committed during Sri Lanka's civil war that ended in 2009, the U.N. High Commissioner for Human Rights said on Monday.

The U.N. investigation into alleged atrocities by government troops and the Liberation Tigers of Tamil Eelam was to have been published in March but was delayed for six months to allow the island's new government to address a failure to bring perpetrators to justice.

U.N. High Commissioner for Human Rights Zeid Ra'ad Al-Hussein, in a speech to the main U.N. rights forum on Monday, welcomed "the vision" shown by President Maithripala Sirisena and commitment of his government.

"But this council owes it to Sri Lankans - and to its own credibility - to ensure an accountability process that produces results, decisively moves beyond the failures of the past and bring the deep institutional changes needed to guarantee non-recurrence," he said.

Sri Lankan Foreign Minister Mangala Samaraweera, who held talks with Zeid on Sunday, is due to address the Geneva forum on Monday.