A recent flare-up of heavy fighting in the east has revived decades-old animosities between Kinshasa and Kigali, with the DRC blaming neighboring Rwanda for a resurgence of a militia called M23.
"Should the M23 continue its well-coordinated attacks against FARDC and MONUSCO with increasing conventional capabilities, the Mission may find itself confronted by a threat that goes beyond its current capabilities," envoy Bintou Keita told the Security Council, referring to Congolese and UN forces.
"Ongoing M23 and armed group activities in eastern DRC threaten to reverse hard-won progress in security and stability in Democratic Republic of the Congo and the region," Keita said.
Rwanda has repeatedly denied backing the rebels, while both countries have accused each other of carrying out cross-border shelling.
Keita asked the Security Council for its help in bringing peace to eastern RDC and urged it and Rwanda to seek a solution.
He said an upcoming African summit in Angola should be used by RDC and Rwanda "to resolve their differences through dialogue."
A primarily Congolese Tutsi militia, the M23 leapt to global prominence in 2012 when it captured the main eastern DRC city of Goma.
It was forced out shortly afterward in a joint offensive by UN troops and the Congolese army.
But the militia has recently made a comeback, clashing with Congolese troops in violence that has inflamed tensions in central Africa and forced thousands of people to flee to neighboring Uganda.