* Says Uganda has denied involvement
* Wants greater involvement of U.N. to fight rebels
By Jonny Hogg
KINSHASA, July 29 (Reuters) - Democratic Republic of Congo's President Joseph Kabila has accused neighbouring Rwanda of backing rebels hostile to his government, saying it was an "open secret" that Kigali was meddling in Congo's volatile eastern borderlands.
Rwanda is under increasing pressure after a United Nations experts' report found it was providing support to the M23 rebels who have fought government soldiers in North Kivu province since April, displacing some 470,000 civilians.
Kigali has repeatedly rejected the allegations and accused the report's authors of failing to verify their information or consult Rwandan authorities.
Kabila commented for the first time on the growing row between the two uneasy neighbours during a rare news conference broadcast on state television on Saturday night.
"As for the involvement of Rwanda...It's an open secret. You know, the whole world knows. There is a report that effectively establishes the presence and active backing from this country to the M23 and to other armed groups," Kabila said.
The president said his government had also requested an explanation from another eastern neighbour, Uganda, of persistent rumours that its soldiers were involved in the fighting.
"The ministry of foreign affairs has specifically asked the Ugandans what is going on and the response is that the Ugandans have nothing to do with it," he said.
Major donors the United States, Britain, the Netherlands and Germany have all suspended some of their financial aid to Rwanda over its alleged backing of the rebels, who have links to Bosco Ntaganda, a warlord wanted by the International Criminal Court on war crimes charges.
Rwanda is often celebrated for its development gains during its long recovery from a 1994 genocide that killed some 800,000 Tutsis and moderate Hutus.
The country is still heavily dependent upon donor support, and Foreign Minister Louise Mushikiwabo on Saturday blasted the donors' aid cut and called for an end to what she described as a "child-to-parent relationship".
Kabila, who has rarely spoken publicly since a controversial election victory last year, said Congo was continuing to seek diplomatic, political and military solutions to the crisis, which risks dragging the region back into conflict.
As part of efforts to defuse tension between Kinshasa and Kigali, foes during years of conflict in Congo, regional leaders brokered a deal earlier this month for a "neutral force" to be set up to take on Congo-based rebel groups.
No details of the plan have been made public but, in theory, the force would target all rebels, including the anti-Kinshasa M23 insurgents and Rwandan Hutu FDLR fighters Kigali says are a threat.
Kabila echoed earlier calls by his information minister for a new mandate for the country's U.N. peacekeeping mission that would include stamping out the armed groups that have destabilised the east for nearly two decades.
"How will this force be made up? We think we've already got a force in this country, the United Nations. Why can't they be transformed, and then other countries could contribute to put this force in place as quickly as possible?" he said.
The U.N. mission, known as MONUSCO, said on Friday that any decision to change its peacekeeping mandate would have to come from the Security Council.
The U.N. already has more than 17,000 troops in Congo as part of its peacekeeping mission. But the force is stretched thin across a nation the size of Western Europe and struggles to fulfil its mandate of protecting civilians as it is.
U.N. helicopter gunships frequently back up outgunned government forces but even that firepower failed to prevent rebels from taking several towns last week.
Diplomats have expressed doubts over whether a move to bolster MONUSCO would be welcomed by Security Council members. (Reporting by Jonny Hogg; Writing by Joe Bavier, editing by Tim Pearce)