BANDA ACEH, Indonesia - Indonesia ordered aid workers and journalists today to declare travel plans or face expulsion from the country's tsunami-devastated Aceh province as authorities moved to reassert control of the rebellion-wracked area.

Security concerns threaten to hamper efforts to deliver aid to the province on the northern tip of Sumatra island, where more than 100,000 people were killed and tens of thousands left homeless or in need. The United Nations has been running the relief effort, appealing to donors attending a conference in Geneva to honor the unprecedented $4 billion in pledges to help victims of the Dec. 26 disaster.

The tsunami devastated a region where separatists have been fighting for an independent state for decades. Indonesia's military chief offered the rebels a cease-fire on Tuesday, matching a unilateral one already declared by the insurgents.

The military has nevertheless warned that rebels could rob aid convoys and use refugee camps as hideouts but has yet to offer evidence to back its claims.

"It is important to note that the government would be placed in a very difficult position if any foreigner who came to Aceh to assist in the aid effort was harmed through the acts of irresponsible parties," the Indonesian government said in a statement.

Asked if those who failed to register with the government before traveling outside the provincial capital, Banda Aceh, would be expelled, Welfare Minister Alwi Shihab said: "I think that is one possibility."

Prime Minister John Howard described Indonesia's demand as "a good idea."

"It is very, very important that in the process of giving full effect to this magnificent international response, that we recognize the difficulties in Aceh, but that we don't overreact to them and we don't dramatize them," he told reporters.

But Australian National University defense expert Clive Williams said the Indonesians wanted to keep close tabs on foreigners to conceal military corruption, not because of rebel danger.

"The big problem with dealing with (the military) in Aceh is that they're involved in a lot of corruption there and the reason I think they don't want people to go to some areas is because they're involved in human rights abuses in those areas," Williams said.

Before the magnitude-9.0 temblor touched off the tsunami, foreigners were banned from the area, and today's demand underlined the unease with which Indonesia has faced the aid operation.

Also today, the U.S. Marines flew a French medical team to the shattered city of Calang by helicopter and delivered supplies to Indonesian troops. Navy crews based on the aircraft carrier USS Abraham Lincoln have flown hundreds of relief missions in the past two weeks.

U.N. agencies said they didn't expect Jakarta's order to affect their operations because their security officers already work in close contact with Indonesia's military.

"It could change the situation of organizations who are moving around like private persons," said Mals Nyberg, a spokesman for the U.N. High Commission for Refugees. "I guess that's what soldiers want to control - that people are moving in conflict areas just like tourists."