Kingsley Amaning, humanitarian co-ordinator for the UN in Chad, said: "We have a seriously deteriorating security situation in Chad and the government's capacity is also diminishing in terms of security response.
"Therefore, along with the [Chadian] government, we are looking at the possibility of putting in place an expatriate, international force that will support government efforts to provide security in the areas where we are operating."
Jan Engeland, the UN humanitarian chief, had earlier met Idriss Deby, the Chadian president, to discuss the situation in the country's long and porous border region with Darfur, where armed groups have been mounting cross-border raids on villages.
Chad army ineffective
"It's very clear that Chad has limitations with its present armed forces being small and its police force being even smaller, and that's why ... we are looking at other methods to try to protect the civilian, refugee and displaced populations," Egeland said.
Chad's army has been stretched
by rebel attacks
UN officials gave no details of which countries might provide soldiers for any mission or how large it would be.
Chad's army has been stretched by rebel attacks culminating in an assault on the capital N'Djamena last month.
Deby accuses Sudan of backing the rebels and has said that if other countries to not solve the Darfur crisis quickly and guarantee security along the border then Chad would no longer be able to shelter Sudanese refugees.
About 200,000 Sudanese have fled into Chad from Darfur, where pro-Khartoum Arab militias are fighting other ethnic groups. The refugees have been joined this year by 50,000 Chadians displaced by fighting between their own government and rebels.
Khartoum and the main rebel faction in Darfur signed a peace deal last week in Abuja.
Egeland said: "I discussed with the president [Deby] how we can all now help to make the Abuja peace agreement a reality. The crisis in Chad has been fuelled by what has happened in Darfur and there will not be peace and security in Chad until we have peace and security in Darfur.
The crisis in Chad has been fuelled by what has happened in Darfur and there will not be peace and security in Chad until we have peace and security in Darfur"
Jan Engeland, the UN humanitarian chief
"I urged the president to do what he can to get all of the rebel groups in Darfur to join the Abuja accord, and he promised to do what he can in this regard."
Attacks on aid workers
Attacks on humanitarian staff - carried out by gunmen believed to range from army defectors and rebels to common bandits - have intensified in Chad's border region with Sudan.
A UN aid worker in the town of Abeche was shot last week by a man dressed in military fatigues who stole her vehicle.
About 70 staff from UN and other aid agencies, representing a quarter of the personnel in eastern Chad, pulled out in mid-April as security fears grew.
Amaning said Deby believed that the best solution was to secure Darfur, but acknowledged that a UN force night not be in place before next year. Sudan's government opposes any UN peacekeeping mission in the region.