Before the ceremony marking the start of the talks, which were approved by the EU foreign ministers on November 21, Rehn will meet Bosnian Prime Minister Adnan Terzic.
The European Commission's Director General for Enlargement, Fabrizio Barbaso, who visited Sarajevo last week, said that the talks could be completed in a year.
PM Terzic believes the talks can be completed by next October when the incumbent government's term expires.
Bosnia's chief negotiator for the talks with the EU is a former ambassador to Washington, Igor Davidovic, while the EU's chief negotiator is Reinhard Priebe.