The decision was taken at a meeting in the Nigerian capital Abuja attended by Chadian President Idriss Deby, Nigerian President Olusegun Obasanjo and African Union commission head Alpha Oumar Konare.
"The three constituent elements of the mediation have decided to harmonise and coordinate their action by putting into place very quickly a liaison office," Chad's mediation spokesman, Ahmat Allami, told AFP.
"The office will be set up in the Chadian capital and will look after collecting information, reviewing how the situation develops on the ground and making the consequent dispositions."
The three leaders decided to send a mission in the near future to check the positions on the ground of the various parties, in line with the decision taken by the summit of heads of state held in Ndjamena in February, Allami said.
"The sending of this mission is even a precondition of a resumption of talks in Abuja."
Peace talks sponsored in Abuja by the African Union between the Sudanese government and the two chief rebel movements in Darfur have been suspended since December because of repeated violations of the ceasefire signed under the mediation of Chad in April last year.
Obasanjo, Deby and Konare met ahead of an African summit on Darfur due to be held in the Egyptian resort of Sharm el-Sheikh