Jahjaga approved Sadiku's appointment at the proposal of Foreign Minister Enver Hoxa after accepting Peci's resignation, Serbian electronic media reported.
Thaci criticised Peci's statement to the press upon taking up office in Belgrade that normalisation of relations could be expected only when Serbia recognised Kosovo, but Peci rejected the criticism.
"I was convinced the state policy on the full normalisation of relations with Belgrade was Serbia's recognition, but it seems this isn't the policy. In such circumstances, I can't continue to work in Kosovo's diplomatic service," Peci said in his letter of resignation.
Under an agreement Serbia and Kosovo reached with the EU's mediation, Peci on Monday assumed office as Kosovo's liaison officer with Serbia at the EU's mission in Belgrade, while Dejan Pavicevic assumed office as Serbia's liaison officer with Kosovo at the EU's office in Pristina.