* African leaders failed to sign the deal last month
* Deal due to be signed in Ethiopia's capital
* Congolese army facing insurgency by M23 rebels
By Michelle Nichols
UNITED NATIONS, Feb 16 (Reuters) - A delayed U.N.-mediated peace deal aimed at ending two decades of conflict in the east of the Democratic Republic of the Congo is due to be signed in the Ethiopian capital Addis Ababa on Feb. 24, the United Nations said on Saturday.
African leaders failed to sign the deal last month due to the concerns of some countries over who would command a new regional force that would deploy in eastern Congo and take on armed groups operating in the conflict-torn region.
The so-called intervention brigade would be contained within the existing U.N. peacekeeping force in Congo, known as MONUSCO.
U.N. Secretary-General Ban Ki-moon sent out invitations on Friday for the Feb. 24 signing ceremony and intended to travel to Ethiopia for the event, his spokesman, Martin Nesirky, said. "All the invited presidents have committed to either be there or delegate power to sign," Nesirky said.
Rwandan Deputy U.N. Ambassador Olivier Nduhungirehe posted on Twitter that the "African Union, the International Conference on the Great Lakes Region, Southern African Development Community Chairs, as well as 10 Heads of States of the region will attend the signing ceremony."
Envoys have said that one of the main reasons the deal was not signed in January was that three countries in the 15-member Southern African Development Community regional bloc - South Africa, Tanzania and Mozambique - felt they did not have enough information on the enforcement brigade.
The creation of an enforcement brigade within a U.N. peacekeeping mission is new for the United Nations, according to officials in the world body. Peace enforcement missions allow the use of lethal force in serious combat situations, while peacekeeping operations are intended to support and monitor an already existing ceasefire, diplomats and U.N. officials say.
A new Security Council resolution would be needed to approve the intervention unit and is likely to be supported by the 15-member council, envoys have said.
U.N. peacekeeping chief Herve Ladsous has made clear that the brigade would fight under the banner of MONUSCO, which means it would be under the same command as regular MONUSCO troops, who conduct patrols and support the Congolese security forces.
But diplomats had said South Africa, Tanzania and Mozambique, which are the most likely candidates to supply the several thousand troops of the brigade, believed it should have its own command.
The countries take the view that MONUSCO has not performed well under its current command, such as when it allowed M23 rebels to occupy the eastern city of Goma last year for 11 days before they withdrew.
REBELS IN MINERAL-RICH EAST
The M23 rebels began taking large swathes of the mineral-rich east early last year, accusing the government of failing to honor a 2009 peace deal. That peace deal ended a previous rebellion and led to the rebels' integration into the national army. They have since deserted the army.
The Congolese army has failed to quell the growing 10-month insurgency by M23, which has dragged Congo's eastern region back toward war and, according to U.N. experts, has received cross-border support from Rwanda and Uganda. Rwanda and Uganda strongly deny the accusations of involvement.
Ladsous said that if approved by the U.N. Security Council, the enforcement unit would be equipped with a three-pronged mandate to prevent the expansion of armed groups in eastern Congo as well as to "neutralize" and disarm them.
It would have the aid of unmanned surveillance drones to hunt down armed militias difficult to spot in the vast territory of eastern Congo. Ladsous said the drones would provide an element of deterrence because the rebels would know they were being watched.
The planned use of drones, is also new for the United Nations, U.N. officials say. Congo's prime minister said on Thursday that the drones could be deployed as early as June.
(Reporting by Michelle Nichols; Editing by Will Dunham)