COLOMBO (AFP) - Sri Lanka appears set to avoid an international inquiry into atrocities committed during its lengthy civil war if a new UN resolution is adopted next week.

Colombo has lobbied successfully for a watering-down of an earlier motion demanding foreign involvement in any probe into human rights abuses during the 37-year conflict.

The draft resolution, which is likely to pass unanimously next week, refers to the importance of having foreign experts involved in a potential investigation, but does not make the condition mandatory.

The initiative was tabled at the UN Human Rights Council in Geneva late Thursday, a week after the publication of a long-awaited UN report that laid bare the horrific barbarity committed by both the army and the separatist Tamil Tiger rebels in the bitter 37-year war.

The report said Sri Lanka's criminal justice system was "not yet ready or equipped" to conduct an independent and credible investigation and called for a hybrid special court to include international judges, prosecutors, lawyers and investigators.

But Sri Lanka has resisted a foreign inquiry, which many members of the island's Sinhalese majority consider an infringement of sovereignty.

The main minority Tamil party the Tamil National Alliance (TNA) said the resolution, initiated by the US and co-sponsored by Sri Lanka, was the "product of a difficult consensus".

"We are acutely aware that some of the language used in the interests of a consensus will not satisfy all victims of the conflict whom we represent and who have reposed their trust in the TNA.

"However, we are of the view that the draft provides a constructive starting point for what will inevitably be a long road to reconciliation," the TNA said in a statement.

The resolution allows Sri Lanka to draw on foreign funding and expertise for a credible domestic investigative mechanism.

Washington dropped its opposition to a domestic-only probe last month, and US Secretary of State John Kerry described the draft resolution as an important step towards a "credible transitional justice process" after the decades-log civil war.

"The United States will remain steadfast in our commitment to walk with Sri Lanka as it takes these important but challenging steps," he said in a statement issued by the US embassy in Colombo.

Sri Lanka's former president Mahinda Rajapakse had been at loggerheads with the US, other Western nations and India, which had censured Colombo over its rights record and failure to ensure accountability for the killings of tens of thousands of civilians.

However, the new government of President Maithripala Sirisena has vowed to ensure ethnic reconciliation and promised to prosecute war criminals.

Prime Minister Ranil Wickremesinghe earlier this week rejected UN rights chief Zeid Ra'ad Al Hussein's call for a "hybrid inquiry" involving both foreign and local judges and prosectors.