Rwanda has threatened to withdraw co-operation with the UN if a draft report criticising its army is published.Kigali said it would reconsider its contributions to UN peacekeeping missions, dismissing claims in the UN report as "insane".
The document accuses Rwanda's Tutsi-led army of killing Hutus in the Democratic Republic of Congo in the 1990s - acts it says may amount to genocide.
Extremist Hutus killed an estimated 800,000 Tutsis in Rwanda during 1994.
But the UN draft report, which was leaked on Friday, says in the years following the genocide, the Tutsi-dominated Rwandan army went into neighbouring Zaire (now DR Congo) and killed tens of thousands of ethnic Hutus - including women, children and the elderly.
It emerged on Saturday that Rwandan Foreign Minister Louise Mushikiwabo had responded to the report earlier this month, sending a strongly worded letter to UN Secretary General Ban Ki-moon.In the letter, obtained by journalists in the US, she criticised the sourcing and methodology of UN investigators.
She concluded: "Attempts to take action on this report - either through its release or leaks to the media - will force us to withdraw from Rwanda's various commitments to the United Nations, especially in the area of peacekeeping."
Rwanda contributes thousands of peacekeepers to the joint UN-African Union mission in the Sudanese region of Darfur, and the commander of the force is a Rwandan.
Analysts say the possible withdrawal of these troops would be a massive blow, especially as it comes at a time of increased violence in Darfur.
Rwandan officials have always said their forces entered the former Zaire, now DR Congo, to pursue the Hutu militias responsible for carrying out mass killings of Tutsis in Rwanda in 1994.
Rwanda's Justice Minister Tharcisse Karugarama told the BBC's Network Africa programme that there was no way Kigali's troops had killed civilians.
"Anybody who would suggest the RPA [Rwandan Army] could do something close to genocide, would be called in this country... mad, insane," he said.
The government was considering what action to take, said Mr Karugarama, who labelled the report a "stab in the back".
The UN report covers the wider conflict in DR Congo, which dragged in several neighbouring countries in what has been called "Africa's world war".
The document lists alleged rights violations by security forces from all the countries involved.
It accuses Congolese troops of involvement in the slaughter of ethnic Hutus - both Rwandan refugees and Congolese Hutus.
The final UN High Commission for Human Rights report is due to be made public in the next few days.