By Elias Biryabarema

KAMPALA (Reuters) - Uganda plans to tell the United Nations it will withdraw its forces from military operations in regional hotspots including Somalia, a security minister said on Friday, in response to U.N. allegations it is supporting Congolese rebels.

Security Minister Wilson Mukasa described the decision as "irreversible" and said another cabinet minister was travelling to New York to explain its position to the world body.

In a leaked report, a U.N. panel of experts last month accused Uganda and Rwanda of supporting the so-called M23 rebel group commanded by Bosco Ntaganda, a warlord indicted by the International Criminal Court nicknamed "the Terminator".

"What we've said and what we are proposing to the UN ... is that we are going to withdraw from our engagements in Somalia, Central African Republic and Democratic Republic of Congo to concentrate on our own security here in Uganda," Mukasa told reporters in Kampala.

Ugandan troops account for more than a third of the more than 17,600 U.N.-mandated African peacekeepers battling al Qaeda-linked Islamist rebels in Somalia.

"I am not aware of any order to withdraw from Somalia but the UPDF is under civilian authority so if an executive decision has been taken to withdraw, that's fine. we'll not stay an extra day in Somalia when we get that order," Felix Kulayigye, spokesman for the Uganda People's Defense Forces, told Reuters.

The AMISOM force has been key to propping up a string of interim governments in Somalia and driving al Shabaab militants from all their key urban strongholds over the last 15 months, including the capital, Mogadishu, and southern port of Kismayu.

A sudden and sharp reduction in the force's numbers, especially in Mogadishu, would risk unraveling the steady security gains that allowed the first presidential elections in more than four decades to be held in the capital in September.

Somalia's poorly equipped and ill disciplined army is more of a loosely affiliated umbrella group of rival militias than a cohesive fighting force loyal to a single president.

Ugandan troops backed by U.S. special forces are also leading the hunt for fugitive Ugandan warlord Joseph Kony in Central African Republic, with some stationed in South Sudan.

"I'm sure that's the rhetoric they might use as a threat, but I can't see them pulling out of Somalia," a Somalia-watching Western diplomat told Reuters.

Uganda has earned significant Western support for deploying its soldiers to a warzone few foreign powers outside the region have the stomach for.

PLAYING TO GALLERY

It also benefits financially for its AMISOM contribution while at the same time a troop presence in Somalia, CAR and South Sudan gives the Ugandan military an enhanced footprint across the region.

"It's just politics and playing to the gallery. They won't pull out. Things will be quietly settled behind closed doors with perhaps future reports not being so critical," said London-based Somali-analyst Hamza Mohamed.

The confidential 44-page report by the U.N. Security Council's Group of Experts, a body that monitors compliance with the U.N. sanctions and arms embargo in place for Congo, said M23 has expanded territory under its control, stepped up recruitment of child soldiers and summarily executed recruits and prisoners.

The report said Rwandan officials coordinated the creation of the rebel movement as well as its major military operations, while Uganda's more subtle support to M23 allowed the rebel group's political branch to operate from within Kampala. Uganda and Rwanda have repeatedly denied the accusations.

(Additional reporting by Drazen Jorgic and Yara bayoumy in Nairobi; Writing by Richard Lough; Editing by James Macharia and William Maclean)