BERLIN (Reuters) - A Franco-German program to develop a European fighter jet will likely be widened to include other countries to lower costs, officials with the German defense ministry and Europe s Airbus said on Wednesday. France and Germany unveiled the plans in July, burying past rivalries as part of a raft of measures to tighten defense and security cooperation. Companies in Britain, Italy and Sweden have expressed interest in participating in the multi-billion-euro program, that is widely expected to be led by Airbus and France s Dassault Aviation. Bertram Gorlo, Airbus Defence and Space s head of key account management for Germany, Austria and Switzerland, told a panel at the Berlin Security Conference that details were still being worked out, but he expected the program to be expanded to include more partners than just Germany and France.  I think ... we will have to ask for the support of other nations,  he said. France and Germany aim to come up with a roadmap by mid-2018 for jointly leading development of the new aircraft to replace their existing fleets of warplanes. Brigadier General Gerald Funke, head of the strategic defense planning and concepts division at the German defense ministry, said development of the next-generation aircraft system would likely begin the 2020s with the goal of seeing it enter into service in 2045. In the meantime, he said Germany was looking at buying an existing aircraft to replace its aging fleet of 85 Tornado jets beginning in 2025. Funke said it would be tough to avoid the national rivalries over jobs and other considerations that plagued earlier international programs like the A400M military transport plane.   In Europe, we re in a world where we still have national interests, industrial interests. And the more partners you have the more complicated it is,  he said.   On the other hand, I m also fully convinced that we will not be able to afford a national solution alone. The key is the will of the partners to cooperate and to find compromise.  Gorlo told the panel that Airbus successfully coordinated with many partners on each of its commercial airliners.  The question is less about the number of partners, it s more about the governance model under which we contract,  Gorlo said. He said the German defense ministry had already expressed interest in setting up a  lead nation  or  lead industry  concept for the new fighter program, which could help ensure a more efficient and streamlined development process. 