The officials told Reuters that a team of about 20 officials was likely to visit Sudan early next month to conduct a feasibility study on the contentious plan.

"Whether the Self-Defence Forces (military) can be dispatched to south Sudan depends on the local security situation to be examined by the research team," a Japanese government official said on condition of anonymity.

If conditions were met, Japan was expected to send up to about two dozen military officials to join the U.N. Mission in Sudan, known as UNMIS, which supervises the peacekeeping operation of some 10,000 personnel in southern Sudan, he said.

Another Japanese government official said Tokyo was studying various plans including the dispatch of several hundred soldiers to southern Sudan on a non-combat mission.

"None of the plans has taken shape fully yet, but they have been discussed in some quarters," he said. "If Japan were to send hundreds of Self-Defence Forces personnel, they are likely to engage mainly in demining."

He said the United Nations had recently sounded out Japan about sending troops to take part in U.N.-led demining operations in southern Sudan.

"It will be a political decision on whether to send Japan's Self-Defence Forces to Sudan," the official said. "The question is 'is it OK to stay away from Africa?'"

The official said Japan would not send troops to the conflict-ridden Darfur region.

"Darfur? That is outside of our scope at this stage," he said.

Japan's pacifist constitution restricts its participation in military activities overseas and forbids the use of force to settle international disputes.

International experts estimate that some 200,000 people have died and 2.5 million been driven from their homes since mostly non-Arab rebels took up arms in Darfur in early 2003, charging the government in Khartoum with neglect.

Earlier this month Japan pledged to extend $200 million in aid for Sudan in the next four years.

Tokyo is eager to take part in U.N. operations in Sudan in an effort to back up its long-running ambition to win a permanent seat on the U.N. Security Council.

Resource-poor Japan, which hosts a conference of 45 African nations next week, wants to play a higher-profile role in the resource-rich region ahead of the G8 summit on the northern island of Hokkaido in July.

"Apart from a permanent seat in the U.N. Security Council, Japan must look at what other countries, particularly China and India, are doing in Africa now," the second official said. "Unless we do something, we will certainly be left behind."

As part of its effort to win the hearts and minds of Africans, Japan announced on Tuesday a plan to double annual foreign aid to Africa by 2012 despite budget constraints caused by the country's bulging public debt.