DR Congo was given a final one-week deadline to take action against two army battalions accused of carrying out at least 126 rapes, diplomats said.
UN peacekeeping chief Herve Ladsous delivered the ultimatum at a meeting with DR Congo Foreign Minister Raymond Tshibanda on Wednesday at UN headquarters, diplomats said.
"[Soldiers] went on a raping and looting rampage in Minova and neighbouring communities."
- Human Rights Watch
The meeting was held as the UN Security Council prepares to vote on Thursday on a resolution setting up an intervention brigade to help the army combat rebel groups in eastern DR Congo.
"The Congo government has been told that the army's actions cannot be accepted and there will be serious repercussions," a UN diplomat said.
UN officials confirmed that Ladsous discussed the rapes with the minister on Wednesday, but gave no details of the ultimatum.
The UN threatened in two letters sent to the government in February to stop working with the army battalions involved unless action was taken over the rapes.
Raping and looting
The UN says at least 126 women were raped in the town of Minova around November 20 as the army retreated from an assault by the M23 rebel movement on the regional capital of Goma. Widespread pillaging was reported around Minova.
The DR Congo army is heavily reliant on UN equipment and military support in its efforts to control the armed groups that hold sway in resource-rich eastern DR Congo.
The notoriously feeble DR Congo army has been much criticised for its brutality against civilians and corruption. UN officials said it "melted away" during the M23 advance last year.
Human Rights Watch says that during a 10-day period, the soldiers "went on a raping and looting rampage in Minova and neighbouring communities."
The UN said in December that its investigators had evidence of at least 126 rapes, and that two soldiers had been arrested for rape and seven for looting around Minova.
But rights groups say no officer has been arrested, and none of the charges have been followed up.
Human Rights Watch said in a report in February that several women told their investigators that "soldiers in official army uniform forced their way into the women's homes at night" demanded money and carried out the rapes.