Kampala — The South Sudanese government has failed to pay the Ugandan People Defence Forces (UPDF) for the past two months, casting doubt on the future of the mission, a well-placed military source told Sudan Tribune on Wednesday.
The non-payment could threaten the deployment of thousands of Ugandan troops still stationed in the volatile areas of Bor and Juba.
The cost of the UPDF's deployment was initially covered by both the South Sudanese and Ugandan governments.
However, the military source, who identified himself as "Ssalongo", said Uganda has now asked South Sudan to foot the bill following mounting criticism from the country's opposition groups.
The UPDF was deployed to South Sudan to fight alongside government forces after conflict erupted in the country in mid-December last year.
The fighting has pitted government troops loyal to president Salva Kiir against rebels aligned with sacked former vice-president Riek Machar.
According to Ssalongo, Uganda is demanding 13 billion shillings (about $5 million)every three months from the South Sudanese government in order to continue their mission.
He said the deployment of Ugandan troops was motivated by fears the conflict may destabilise the neighbouring regions, leaving Uganda vulnerable to security threats.
"Being in South Sudan it is for betterment of Uganda security. If our forces withdraw from that conflicts Ugandan citizens will be hit so much and we want our people to be safer from killing," said Ssalongo.
South Sudan's defence minister, Kuol Manyang Juuk, earlier admitted billing Uganda for its army's operational costs.
On a visit to the Ugandan capital, Kampala, South Sudan's vice president James Wani Igga, denied his government was responsible for funding the Ugandan military's mission in South Sudan.
Igga also told group of students at a rally in Kampala that the Ugandan government would bear its own military expenses, not South Sudan.
Sudan has accused Uganda of providing military support to Sudanese rebels seeking to oust Sudanese president Omer Hassan al-Bashir from power, a claim the Ugandan government dismissed as "rubbish".
It has counter-accused Sudan of supporting rebels from the notorious Lord's Resistance Army (LRA).
Uganda has come under heavy international pressure to withdraw its troops from South Sudan amid fears their presence was further destabilising the region.
However, Uganda has maintained that it would not pull out unless neutral protection forces were deployed in the country.