"The first condition for that is the earliest possible creation of a stable government," the statement said.
A senior political source told Reuters: "This serves only to set the scene for serious coalition talks. Both camps need more time to figure out their best options. The final talks will be held between Tadic and Kostunica themselves."
The parties scheduled their next meeting for March 7, when they will discuss "the structure of the future coalition and principles of the government's composition".
"Kostunica has not made up his mind yet on what he really wants - whether to remain prime minister and decisively deal with all the challenges," the senior political source said.
Kostunica has taken a nationalist line in Serbia's dealings with the West, despite a freeze on talks imposed by the European Union last May for Serbia's failure to hand over Ratko Mladic, the top war crimes fugitive and the former Bosnian Serb commander.
Kostunica has in recent months established himself as champion of a bi-partisan political front which rejects the Western-backed plan to give independence to the Albanian-dominated breakaway province of Kosovo, excising the territory from Serbia.