* Air force investigating oil leaks, hydraulics
* Company says to support military investigation
* Ministry says A400M incident "very aggravating"
* Unclear if new technical issue for troubled programme (Adds details, background)
By Andrea Shalal
BERLIN, Feb 8 (Reuters) - Germany is investigating whether engine trouble in an Airbus A400M, which broke down during a visit by Germany's defence minister to Lithuania, represents a new technical problem for the plane, Europe's largest defence project.
Germany's defence ministry described Tuesday's incident, which follows years of delays and technical issues for the A400M, as "very aggravating".
Defence Minister Ursula von der Leyen was on her first foreign trip on the plane, which was meant to showcase the capabilities of the multinational programme. She had to fly home on another older plane, leaving the A400M behind.
A German defence ministry spokesman said the air force was investigating oil leaks discovered in one of the plane's four engines during a routine check after arrival in Lithuania.
"The company knows what needs to be done. We want a reliable and efficient aircraft," the spokesman said on Wednesday.
Airbus, which has already written off over 5 billion euros on the programme after gearbox problems and fuselage cracks, said it was doing all it could to help with any analysis required, adding that an Airbus pilot was standing by to help return the defective aircraft to Germany.
"We are shocked and deeply regret that the defence minister and her delegation suffered significant travel consequences as a result of the breakdown of an A400M," an Airbus spokesman said.
The A400M programme is years behind schedule, with Germany's share of the costs having risen to 9.6 billion euros ($10.2 billion) from an initial estimate of 8.1 billion.
Germany is the largest customer for A400M, which was initially developed for seven European NATO nations at a cost of 20 billion euros.
The latest episode followed a report that Germany hoped to maintain access to more A400M planes by signing pooling agreements with several countries, instead of selling on 13 of the 53 aircraft it is due to buy.
German officials said new aircraft often experienced "growing pains" but it was unclear if the latest issue revealed a new technical challenge. A German air force spokesman said investigators were focused on the engine's hydraulic system, but had no further details.
The defence ministry spokesman said Germany had a good contract with Airbus that allowed it to demand compensation for delays and other issues.
Germany only took delivery of the defective A400M - the first delivered with self-defence equipment - in December.
A second was delivered one or two weeks ago, and German sources said they expected to receive eight or nine more A400M aircraft this year.
Airbus said it had made great strides on the programme over the last year, with the total A400M fleet now having logged more than 40,000 flight hours. (Editing by Michael Nienaber and Alexander Smith)