Spohr told the Rheinische Post (link in German) on Wednesday that that the group had earmarked €1.5 billion ($1.78bn) for takeover-related costs, such as taking on Air Berlin employees.
It said last month that negotiations with Lufthansa and EasyJet would continue until Friday.
Lufthansa, Germany's largest airline, is set to buy Air Berlin's Niki leisure unit, its LG Walter regional airline and some additional short-haul aircraft, Reuters reported. As part of the deal Lufthansa will take over Air Berlin's low-priced leisure airline Niki, its LG Walter regional airline as well as 20 additional aircraft - bringing the total to around 80 planes.
Meanwhile, unions have complained that many of Air Berlin's staff faced an uncertain future despite promises when talks with Lufthansa and Easyjet began that most would find jobs with the bidders.
The move drew fire from European competitors, which accused the German government of unfairly helping the Frankfurt-based Lufthansa get a leg up on the its EU rivals by offering Air Berlin a lifeline.
HSBC analysts lifted their target share price to 29 euros from 25 euros (£22.38), citing the imminent agreement with Air Berlin, a new multi-year labour deal with pilots announced this week and a positive trading performance this year.
Air Berlin, the second largest carrier in Germany, will end all operation of its flights during October, capping a tumultuous summer for carriers in Europe.