* Kabila, Kagame endorse Great Lakes region initiative
* Deal foresees international force to take on insurgents
* East Congo is tinderbox of ethnic and political violence
By Pascal Fletcher and Aaron Maasho
ADDIS ABABA, July 15 (Reuters) - The presidents of Democratic Republic of Congo and Rwanda on Sunday threw their weight behind a regional pact to eliminate armed rebels in eastern Congo, signing the document and holding rare face to face talks.
Along with other leaders from the Great Lakes region, Congo's Joseph Kabila and Rwanda's Paul Kagame put their signatures to an accord that foresees the creation of an international military force to take on multiple insurgencies in the eastern Congolese provinces of North and South Kivu.
Uneasy neighbours Congo and Rwanda, which have gone to war with each other in the past, have often swapped accusations about backing rival rebel groups, a charge that both Kigali and Kinshasa deny.
Ugandan President Yoweri Museveni, who also attended the Great Lakes meeting on the sidelines of an African Union summit in Addis Ababa, described the atmosphere between the Congolese and Rwandan leaders as "excellent, amicable".
"There was no fighting," Museveni joked to reporters. Before joining the other regional leaders, Kabila and Kagame held a separate one-on-one meeting for more than half an hour, also at AU headquarters, aides said.
The agreement, originally initialled by Great Lakes region foreign ministers on Thursday, proposes a military response to an offensive by Tutsi-led M23 rebels in east Congo's turbulent borderlands, which are a political and ethnic tinderbox.
Rebel advances this month sent the Congolese government army fleeing in droves, displaced thousands of civilians, killed an Indian U.N. peacekeeper and stoked tensions between Congo and Rwanda. Congo accused the Rwandan army of directly equipping and supporting the M23 rebellion.
Rwanda's government strenuously denied the accusations despite evidence provided by U.N. experts supporting allegations that high-level military officials in Kigali were supporting and supplying the rebellion in eastern Congo.
Kabila, Kagame and the other Great Lakes presidents condemned "in the strongest terms the actions of the M23 and other negative forces operating in the region and support the efforts deployed by the government of the DRC for the restoration of peace and security in North Kivu province," according to the declaration from the meeting seen by Reuters.
Endorsing Thursday's security pact, the leaders also condemned a separate eastern rebellion by predominantly Hutu insurgents and agreed to "work with the AU and the UN for an immediate establishment of a neutral international force to eradicate" all armed groups in eastern Congo.
"No support should be given to any negative force to destabilise the region and eastern Congo in particular," the declaration by the presidents of the International Conference on the Great Lakes Region, said.
Eastern Congo's enduring conflict, which has killed, maimed and displaced several million civilians over nearly two decades, has its roots in Tutsi-Hutu ethnic and political enmities dating back to the 1994 Rwandan genocide.
Later invasions of Congo by Rwandan forces and Kigali's backing of Congolese rebels fuelled two crippling wars.
WHO WILL SUPPLY THE TROOPS?
The M23 rebellion takes its name from a 2009 peace accord the rebels say was violated by Kinshasa. It has been swelled by hundreds of defectors from the Congolese army who walked out into the bush in support of fugitive Congolese General Bosco Ntaganda, wanted by the International Criminal Court on war crimes charges.
While welcoming the regional pact against armed rebels in eastern Congo, diplomats from major Western backers of Congo and Rwanda, such as the United States, have questioned where the troops for the "neutral international force" will come from.
The U.N. has a peacekeeping mission of more than 17,000 in the Congo but has often been hard pressed to halt fighting and protect civilians in the vast, unruly central African state which produces gold, copper, tin, diamonds and other minerals.
Addressing a plenary session of the AU summit on Sunday, AU Commission chief Jean Ping said the African body was willing to contribute to the anti-rebel force.
Diplomats said the operating mandate of the U.N. peacekeeping mission in Congo, MONUSCO, could also be strengthened so it could take more robust action against the eastern Congolese insurgents.
The encounter between Kabila and Kagame was the second successful rapprochement between feuding neighbours achieved by the heads of state at the Addis Ababa summit.
On Saturday, the summit also brought together the presidents of Sudan and South Sudan, raising hopes that they could peacefully settle through negotiations border and oil disputes that had pushed them close to war in April.
(Reporting By Pascal Fletcher and Aaron Maasho; editing by Patrick Graham)