Sri Lanka is "deeply unhappy" at a move by UN chief Ban Ki-moon to name a panel to look into alleged war crimes committed during the final months of the island's civil war, an official said om Monday.
Colombo repeated President Mahinda Rajapakse's protest to Ban in March that the panel was "unwarranted and uncalled for," a senior government official said, declining to be named.
"The government is deeply unhappy with the appointment of this panel and made it very clear to the secretary-general himself and other UN representatives that this is unwarranted and uncalled for," the official said.
Ban is due to name a three-member panel on Monday to advise him on the Sri Lankan military campaign that crushed the separatist Tamil Tiger rebels after 37 years of fighting. The government has been dogged by war crime allegations in the wake of the campaign.
The exact mandate of the panel is not yet clear, but diplomats said the team could be a precursor to a full-blown war crimes investigation.
The UN has said that at least 7,000 ethnic Tamil civilians perished in the first four months of last year, just before the government claimed final victory over the Tigers.
The military has also been accused of executing surrendering rebels.
Rajapakse warned Ban in March that the appointment of the panel would compel Sri Lanka to take "necessary and appropriate action," but did not specify what that would be.
Sri Lanka has insisted that no civilians were killed by its troops and has refused to submit to any international probe even as rights groups and Western nations demand an independent investigation.
Colombo managed to stave off censure at the UN Security Council last year thanks to the support of Russia and China, close allies and key suppliers of military hardware to Sri Lanka.
Sri Lanka's major aid donor Japan has backed Ban's move and said it would be "useful" in reconciling Tamils and the ethnic majority Sinhalese.
Yasushi Akashi, special peace envoy to Sri Lanka, ended a five-day visit on Sunday urging Colombo to agree to the UN panel, but said he detected a "lack of flexibility and openness" in Sri Lanka's attempts to promote reconciliation.