Tshisekedi urged the international community to help Congo restore peace and state authority in this part of the country.
He again accused Rwandan authorities of supporting the M23. Rwanda denies backing the rebels.
Rwanda's President Paul Kagame said in January that he would no longer accept refugees from Congo.
Geneva
Democratic Republic of Congo's President Felix Tshisekedi said on Monday that a conflict with rebels in the east of the country could disrupt preparations for general elections scheduled for December 20.
Congo's electoral commission started registering voters on February 17 in North Kivu province, parts of which are occupied by the M23 rebel group, a Tutsi-led militia that has been waging an offensive against Congolese troops for almost a year.
The fighting has displaced hundreds of thousands of people, raising concerns about the country's ability to prepare for the parliamentary and presidential elections later this year.
"The persistence of the war in the east of our country risks jeopardising the electoral process, which is already underway, due to a massive displacement of people from combat zones, the insecurity and the inaccessibility of these areas," Tshisekedi told the UN Human Rights Council session.
Restore peace
The DRC president urged the international community to help Congo restore peace and state authority in this part of the country.
He again accused Rwandan authorities of supporting the M23. Rwanda denies backing the rebels.
Three Congolese and foreign electoral experts told Reuters the electoral commission could postpone the polls. It has already delayed the deadline for voter registration twice in more than a dozen western provinces due to technical problems.
Registration has so far been impossible in the territory under M23 control in North Kivu, one of Congo's most populous provinces.
The Congolese government has asked the UN High Commissioner for Refugees (UNHCR) to hold discussions between Congo, Rwanda and the UN agency about repatriating refugees, Tshisekedi added.
Rwanda's President Paul Kagame said in January that he would no longer accept refugees from Congo.
There are around 72,200 Congolese refugees in Rwanda and almost 210,000 Rwandan refugees in Congo, according to the UNHCR.