The DRC has been floating joint military operations to "eradicate armed groups."
The UN on Friday ruled out giving any support to countries neighbouring DR Congo if they intervene militarily in the east of the country, which is plagued by militia violence.
The prospect of joint military intervention by DR Congo and its neighbours has surfaced in the light of a meeting of senior military officials from five Great Lakes nations.
According to a letter seen by AFP, the DRC has been floating joint military operations to "eradicate armed groups."
But Leila Zerrougui, the head of the UN's peacekeeping mission in the Democratic Republic of Congo (DRC), said the organisation could not lend support for foreign forces intervening in the country.
"We have no mandate to support foreign forces who enter the DRC," she said on the UN station Radio Okapi.
"Our mandate is to support the Congolese army."
"The best way to protect the civilian population is to restore state authority (to the region), to restore justice, the police and the army," she said, adding that rights had to be respected.
The UN's mission in the DRC, Monusco, is one of its biggest deployments. Some 17,000 blue helmets are in the country.
The meeting in the eastern DRC city of Beni, which continued on Friday for a second day, gathered military chiefs from Burundi, the DRC, Rwanda, Tanzania and Uganda.
Monusco spokesman Florence Marchal said Monusco and the US military command for Africa, Africom, were taking part as "guests and observers."
Among the militias troubling the Kivu region are the Allied Democratic Forces (ADF), an Islamist-rooted Ugandan armed group, and the Democratic Forces for the Liberation of Rwanda (FDLR).
Both groups have been blamed for a string of atrocities in eastern DRC.
But they are also a source of political friction between the DRC and its neighbours because of their cross-border nature.
Kinshasa has in the past accused neighbouring governments of seeking to destabilise it. These governments in turn have said DRC is a haven for groups that oppose them.