The UN has withdrawn its backing for a planned offensive against rebels in eastern Democratic Republic of Congo after the government refused to sack two generals, a spokesman has said.
UN troops could not join the offensive because the generals were accused of human rights abuses, he added.
The planned offensive was aimed at disarming the FDLR rebels who are seen as a threat to regional stability.
DR Congo’s government has not yet commented on the UN’s decision.
It has previously said that it chose its best soldiers to fight the FDLR, and it will not take instructions from the UN.
One of the men chosen to lead the operation, Gen Bruno Mandevu, is on a UN “red list” over 121 alleged human rights violations, including summary executions and rapes, according to Reuters news agency.
The government says he is innocent until proven otherwise.
UN spokesman Nick Birnback told BBC News-day that there was “credible evidence” against the generals and “until such time as that has been cleared, we won’t work directly with them”.
The UN has more than 20,000 troops in DR Congo to help the government restore order in the mostly lawless east.
The FDLR was formed by Rwandans who fled to DR Congo after the 1994 genocide in Rwanda.
Rwanda sees the FDLR as a threat to its stability and, along with the UN, has repeatedly demanded its disarmament.
It has twice invaded DR Congo, saying it is trying to hunt down the militiamen who took part in the genocide.
Rwanda’s critics say many FDLR fighters are too young to have taken part in the genocide.
The FDLR has been accused of recruiting child soldiers, rape and systematic looting.