Uganda said Saturday it welcomed US combat troops to help its forces battle the Lord's Resistance Army, a brutal rebel force whose leaders are international war-crime 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 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."

LRA rebels are accused of terrorizing, murdering, raping and kidnapping tens of thousands of people in a 20-year war in northern Uganda.

However, in recent years they have shifted to regional nations, causing havoc and forcing civilians to flee their homes.

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."