UN peacekeeping chief Herve Ladsous said a delay in signing the agreement was not over substance but a matter of process with other regional nations.
UN diplomats said southern African nations that are to be part of the agreement wanted more time to examine the final draft.
The UN has more than 17,700 UN peacekeepers and over 1,400 international police in Congo, but they did little to protect civilians as M23 rebels swept through eastern Congo last year and seized the key city of Goma.
Human Rights Watch said this week that Congolese government soldiers and M23 rebels "raped scores of women and committed other war crimes during the rebels' occupation of Goma".
Mr Ladsous said the UN peacekeeping mission has confirmed 126 rapes, identified many of the perpetrators, and is urging Congolese authorities to prosecute them.
As a result of talks with countries in the region and key organisations, he said there is growing agreement on the need to create an "intervention brigade", which would be part of the UN force, and give it a mandate to rein in, neutralise and disarm rebel groups in the east.
The peacekeeping chief said he briefed the UN Security Council behind closed doors on Tuesday on the possibility of deploying intervention troops.
"We will see over the next two weeks how this can materialise," he said, stressing again that intervention troops would be able to "take enforcement action on those armed groups which have been one of the direct causes of the massive suffering of the population in the region".
The peace agreement had been expected to be signed at the African Union summit in Addis Ababa, Ethiopia on January 28 by eight countries: Congo, the Republic of Congo, Rwanda, Uganda, Burundi, South Africa, Angola and Tanzania.