UN troops have been in DR Congo for 10 years
The UN envoy to the Democratic Republic of Congo says a joint military operation against rebels will be concluded at the end of this month.
Alan Doss told the UN Security Council that the campaign in the east of the country had "largely achieved" its goal of weakening the Rwandan Hutu rebels.
The operation was criticised by rights groups, who accuse Congolese government troops of killing and raping civilians.
UN experts had said the campaign failed to dismantle militia infrastructure.
But Mr Doss declared that had not been the objective, as the rebel group, the Democratic Forces for the Liberation of Rwanda (FDLR), is deeply entrenched in eastern DR Congo.
He did acknowledge there was a dilemma at the heart of the peacekeeping mandate to both protect civilians and work with an undisciplined Congolese army.
Earlier this week, Human Rights Watch said the offensive had seen 1,400 civilians murdered this year by both Congolese troops and rebels.
Mr Doss told the Security Council that Congolese troops backed by the UN force "will now concentrate on holding ground recovered from the FDLR and preventing attacks on civilians in areas of vulnerability".
The FDLR has been active in eastern DR Congo, especially North and South Kivu, for 15 years.
Some of its older members are accused of taking part in the 1994 genocide in neighbouring Rwanda, which targeted the Tutsi minority and claimed about 800,000 lives.
Mr Doss said during the first half of next year UN officials would propose a realistic plan for reconfiguring the 21,000-strong peacekeeping force in Congo, known as Monuc, which has been deployed in the country for the past 10 years.
Diplomats say a draft resolution submitted to the Security Council would extend the peacekeepers mandate by five months.
At that point, the idea would be to begin phasing them out of combat and into a programme to reform the army and police forces, says the BBC's Barbara Plett at the United Nations in New York.