The president of Chad has cut diplomatic ties with Sudan, which he accuses of backing rebels trying to overthrow him.
President Idriss Deby also threatened to expel 200,000 Sudanese refugees from the war-torn Darfur region, unless the international community stops what he called Sudan's efforts to destabilize his country.
Mr. Deby spoke Friday, one day after his forces fought off a rebel attack on the capital.
Sudan's Foreign Minister, Lam Akol, says his country had nothing to do with the attack.
However, the Central African Republic, which lies south of Chad, said it is closing its border with Sudan, after it spotted rebels crossing its territory between Chad and Sudan.
The United States says it has grave concerns about Chad sealing off its borders with Sudan, arguing it will only exacerbate the situation.
A U.S. State Department spokesman, Sean McCormack, said the United States is also worried about the impact on refugees as well as access to refugee camps on both sides of the border.
President Deby has declared victory over the rebels, who assaulted the capital after a week of attacks in other parts of Chad.
Leaders of the rebel group, the United Front for Change, have vowed to continue their campaign to topple Mr. Deby. Chad's government calls the rebels mercenaries hired by Sudan.
The United Nations has evacuated all non-essential staff and the personnel of various aid agencies from N'Djamena. The U.N. World Food Program heads up efforts to feed the Sudanese refugees, who fled Sudan's war-torn Darfur region.
Meanwhile, the government says it will stop oil production on Tuesday if it cannot resolve a dispute with the World Bank over the use of oil revenues.
Chad's human rights minister, Abderamane Djasnabaille, issued the warning after a cabinet meeting Friday.
In January, the World Bank suspended $124 million in aid to Chad and froze a London-based account that holds the country's oil profits. Chad's human rights minister says his country wants the London account unblocked.
The dispute arose after Chad's parliament abolished a fund that reserved 10 percent of its oil revenue to help the poor. Parliament said one of the main ways the money could be spent instead is on security.
The World Bank had helped Chad finance a key oil pipeline on the condition that Chad use oil revenue to improve living standards.
Chad produces an estimated 225,000 barrels of oil per day through a consortium led by ExxonMobil.
Some information for this report provided by AP, AFP and Reuters.