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.
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 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.
Information for this report is provided by AP, AFP and Reuters.
