Sudan has accused Chad of assisting Darfur rebels in their fight against the government.
Chad's foreign ministry rejected the claims Thursday. It says Sudan's allegations are unfriendly because Chad has contributed to the peaceful resolution of the Darfur crisis through its mediation with the African Union.
Sudan's accusations come less than a week after Chad accused Khartoum of using Chadian army deserters to fight a small rebel group in Darfur.
Hundreds of thousands of refugees from Darfur have fled into Chad since the Sudanese conflict erupted more than two years ago.
Some information for this report provided by AP and Reuters.