BERLIN (Reuters) - Germany and France will launch a program this month to develop a successor to their aging marine surveillance aircraft, amid growing concern about increases in Russian submarine patrols.

German Defence Minister Ursula von der Leyen and her French counterpart, Florence Parly, plan to sign a letter of intent about the new “Maritime Airborne Warfare System” at the Berlin air show on April 27, the German navy said on its website.

The two countries agreed last July to seek a “European solution” to replace existing marine surveillance planes, and develop a road map to that end by mid-2018. The letter of intent formalizes those plans and paves the way for both countries to harmonize their military requirements for the maritime mission.

The initiative is part of a larger drive by France and Germany to increase their cooperation on defense programs, including efforts to develop a new European fighter jet.

Germany now uses the P-3C Orion built by Lockheed Martin Corp to patrol large swathes of ocean for submarines and other potential threats, while France operates the Atlantique 2, or ATL2, produced by Dassault Aviation in the 1980s.

Elisabeth Braw, a London-based fellow at the U.S. Atlantic Council think tank, said the new Franco-German projects might succeed better than the A400M military transport plane and other past projects because they did not involve as many states.

But she said it was unclear if European industry had the expertise to develop a new fighter jet that could beat U.S. rivals in future international competitions.

“Even Airbus is not 100 percent successful, so to go from there to a new fighter jet, it’s a very long leap of faith,” she said.

German navy officials were not immediately available for further comment on the program, or how it will tie into an effort by eight NATO allies, including France and Germany, to cooperate on “multinational maritime multi-mission aircraft capabilities.” The program also includes Canada, Poland, Italy, Spain, Turkey and Greece.

NATO members are modernizing and upgrading military equipment in the wake of increasingly assertive actions by Russia, including a high level of submarine patrols not seen since the end of the Cold War.

France and Germany will also take a “significant first step” on development of a new European fighter jet at the Berlin air show, France’s Parly told French media on Thursday.

In addition, they will display for the first time a life-sized model of the planned “Eurodrone,” a program that also involves Italy and Spain.

Germany on Friday underscored its commitment to European defense integration, but said it also planned to be more assertive about seeking waivers from European Union regulations that require Europe-wide competition for defense equipment.

Defence Ministry spokesman Holger Neumann told a government news conference the step was part of a larger effort to improve Germany’s weapons buying system amid reports of shortfalls in military equipment and personnel.