* No time frame for deployment, force will cost $100 mln
* SADC calls for stronger UN peacekeeper mandate
* Eastern Congo ravaged by two decades of violence
* Fighting fuelled by competition for mineral wealth
By Fumbuka Ng'wanakilala
DAR ES SALAAM, Dec 8 (Reuters) - Southern African nations pledged on Saturday to provide 4,000 troops for a neutral force to be deployed in eastern Congo where rebels have waged an eight month-long rebellion, the South African Development Community (SADC) said.
The regional bloc also urged the United Nations to strengthen the mandate of the U.N. peacekeeping force that was forced to give up defending the city of Goma last month when Congolese troops fled from advancing M23 rebels.
"This summit strongly condemned the M23 and all its attacks on the civilian population ... as well as its abuses of human rights," said Tomaz Salomao, reading a communique at the end of a summit in Tanzania's commercial capital, Dar es Salaam.
Under the arrangement, Tanzania will send a battalion of soldiers and the SADC bloc will "activate" a standby brigade of about 3,000 soldiers by mid-December.
Tanzanian President Jakaya Kikwete, however, said the standby brigade's deployment would be conditional on member-states coming up with both the troops and funding.
The idea of a neutral force, which will cost an estimated $100 million, was first mooted several months ago but disagreement over where the troops should be drawn from has hindered its formation.
There has been a lull in the fighting in Congo's eastern borderlands after the rebels pulled out of Goma earlier this month, a move they said Congolese President Joseph Kabila had demanded for peace talks to proceed.
Kabila and South African President Jacob Zuma were among the six heads of state at the summit.
The rebels, widely believed to be supported by Rwanda, pose the biggest threat to Kabila in years. Rwanda strongly denies any involvement in the latest cycle of violence in Congo's mineral-rich border region.
The ease at which M23 marched into Goma was seen as a major embarrassment for the U.N. MONUSCO peacekeeping force.
The force said its helicopters had fired hundreds of rockets at the rebels but was powerless to beat them back once the Congolese army abandoned its positions.
FOCUS ON TALKS
Tanzania's government spokesman, Assah Mwambene, said SADC wanted a more robust mandate for MONUSCO.
"SADC member states want the mandate of the U.N. peacekeeping mission ... to be changed from the traditional peacekeeping role to peace enforcement activities to enable it to engage M23 rebels militarily if the need arises," Mwambene told Reuters.
Amani Kabasha, a spokesman for M23's political arm, told Reuters the rebels had no problem with a SADC-led force.
"But we think the major focus should be put on the negotiations in Kampala, not on the neutral force. It's peace talks that will resolve our problems with Kabila, not this neutral force," Kabasha said from Bunagana in Congo.
M23 is led by members of a previous rebel movement who were brought into the Congolese army and then mutinied eight months ago, accusing the government of violating the deal. However, they are now demanding wider political reform, claiming broad popular support.
A rebel delegation is due to meet with a team from the Kinshasa government, perhaps as early as tomorrow, in the Ugandan capital, Kampala, Kabasha said. Those talks, though, are expected to deal only with a framework for later negotiations. (Additional reporting by Elias Biryabarema in Kampala; Writing by Richard Lough; Editing by Myra MacDonald)