* Rebel commander fled to Uganda where deal to be signed

* M23 said Congo reneged on earlier peace agreement

* Congo's army routed rebels with U.N. force backing

* Analysts sceptical this deal means sustained calm

By Elias Biryabarema

KAMPALA, Nov 11 (Reuters) - Congo and defeated M23 rebels are to sign a peace deal on Monday to end a 20-month revolt in the east of the vast African nation, where other militias still roam and millions are destitute despite great mineral wealth.

The rebels, who accuse Kinshasa of reneging on an earlier deal with another movement of ethnic Tutsis, gave up their insurrection last week after the Democratic Republic of Congo's army backed by a U.N. force routed them from their hideouts.

The M23's military commander, Sultani Makenga, fled and is now being held in neighbouring Uganda, which has been trying with international support to mediate an end to the fighting.

The peace deal is to be signed in Uganda's capital Kampala.

Makenga's surrender is a major achievement for Congo as it struggles to impose order and a vindication for the world powers which backed a U.N. force of African troops that was given a strong mandate to intervene to try to break a bloody deadlock.

But analysts are sceptical there will be sustained peace in an area devastated by two decades of conflict that has killed millions and left others in grinding poverty despite underground deposits of gold, diamonds and other valuable minerals.

"I don't think there is a track record in the DRC of these sort of issues being resolved," said Brian Dlamini, a country risk analyst for Rand Merchant Bank in South Africa.

"The DRC is a country of many countries," he said.

Kinshasa has limited ability to exert its authority over one of Africa's biggest nations. There is no tarmac road connecting the capital to the main eastern town of Goma.

Signalling broad international support for a deal, a Ugandan official said Monday's signing would be attended by representatives from the African Union and the United Nations.

But regional rivalries could still unsettle any shaky peace.

'VITAL FOR RWANDA'

U.N. experts, the United States and others have long accused Rwanda of backing the M23, despite Kigali's vigorous denials. Aid cuts and other pressure from donors were seen as one reason why Rwanda may have backed off from trying to rescue the M23 when the U.N.-backed Congolese army closed in, analysts say.

But a regional diplomat, in remarks widely echoed, said neighbouring Rwanda would not easily abandon interests in east Congo, which it says is still a haven for Hutu rebels behind Rwanda's 1994 genocide that killed Tutsis and moderate Hutus.