Uganda and its neighbours hailed Saturday a US offer to send combat troops to help battle a brutal regional rebel force whose leaders are international war-crimes fugitives.

"We welcome this gesture -- it has been well overdue," said Uganda's acting foreign minister Henry Okello Oryem.

US President Barack Obama said Friday that 100 troops would help Uganda track down Lord's Resistance Army rebel chief Joseph Kony and other senior LRA leaders, but warned they would not lead the fighting themselves.

"For 20 years, the government of Uganda has been pleading with our American and European friends to help in the LRA problem, because these are international terrorists," Oryem said.

"We wanted our friends to help in providing technical support -- such as intelligence -- because they have the best."

Fighting between the rebels and Ugandan forces in a 20-year war claimed the lives of tens of thousands of people and saw nearly two million displaced.

However, in recent years the LRA have shifted from northern Uganda to regional nations, causing havoc in a bloody campaign of rape, murder and mutilation.

The mostly special operations forces could deploy in Uganda, South Sudan, the Central African Republic and Democratic Republic of Congo, subject to approval of regional governments, Obama said in a message to Congress.

Uganda's defence spokesman Felix Kulayigye said the first batch of US troops were already in Uganda.

"Some of the forces are already in the country," Kulayigye said. "Their approach is regional -- DR Congo, Central African Republic, South Sudan and Uganda. How far they will go depends on the cooperation arrangements."

Washington has provided more than $40 million in logistical support, equipment and training to counter-LRA operations by armies in the region since 2008, according to State Department officials.

Kony, an International Criminal Court fugitive believed to be hiding in Central African Republic, is accused of extreme brutality, including seizing boys as child soldiers and girls as sex slaves and porters.

In 2009, Congress enacted a law expressing support for increased US efforts to mitigate and eliminate the threat posed to civilians by the LRA.

Neighbouring South Sudan said it also supported the US deployment.

"Any support to tackle the LRA is a good move," said army spokesman Philip Aguer, who said suspected LRA fighters had launched attacks against communities along the country's western border in recent weeks.

"South Sudan is already working with Uganda's army in operations against the LRA, and we will be pleased to work with anyone who can help us combat the threat," he added.

Large swathes of South Sudan's key breadbasket region of Western Equatoria have been left unfarmed for fear of attack by the jungle guerrillas, Aguer said.

"We have large communities whose lives are ruined by these rebels, so the sooner we can end this once and for all will be something we will look forward to."

Lambert Mende, DR Congo government spokesman, said the move was supported because what the LRA had done to the country "is beyond comprehension".

"In repeated meetings we have called for collaboration between the concerned governments... this action is in response to that call," he said.

Deputy defence minister Jean-Francis Bozize equally welcomed the US aid, saying the damage done to his country by the rebels is "truly tragic."

"The Central African Republic today more than needs external assistance like that of United States," he said.

"Many hundreds of our people have been killed, others kidnapped or displaced, their homes ransacked, destroyed, their possessions looted. It is unbearable," he added.

But supporters of the LRA claimed a military solution ignored the root causes of marginalization in northern Uganda, that they say provided the grievances for the rebellion in the first place.

"You can cut off the head of Kony and kill the commanders, but that won't help the people of northern Uganda, marginalized over so many years," said Justine Labeja, who represented the LRA in failed peace talks in 2006.

But Ugandans in the northern Gulu district, once one of the areas worst affected by the conflict, said hunting down LRA commanders would help them move on with their lives.

"This effort should have come years ago, but it is better late than never," said Bosco Odongpiny, a resident of Koch Goma in Gulu.

"Without capturing Kony and the remaining commanders, we in northern Uganda will always feel insecure."