BERLIN (Reuters) - The U.S. military has approved Lockheed Martin Corp's LMT.N new CH-53K heavy-lift helicopter to fly at the Berlin air show next April, according to two sources familiar with the program.

Lockheed Martin's logo is seen during Japan Aerospace 2016 air show in Tokyo, Japan, October 12, 2016. REUTERS/Kim Kyung-Hoon

It will mark the CH-53K’s international debut at time when a German helicopter competition could start heating up again, said the sources, who were not authorized to speak publicly.

The German defense ministry is nearing the kickoff of a competition valued at nearly 4 billion euros ($4.7 billion) between two U.S. helicopters - Lockheed's massive Sikorsky CH-53K and the smaller Boeing Co BA.N CH-47 twin-rotor helicopter - to replace its existing fleet of CH-53G aircraft.

A formal decision on how to structure the competition has stalled as Chancellor Angela Merkel’s conservatives try to forge a ruling coalition with the pro-business Free Democrats and the Greens, an endeavor that could take until the end of the year.

Military sources expect the program to proceed only after a new government is in place, but say it could be delayed further if the current defense minister, Ursula von der Leyen, is replaced. Any successor would want to review major weapons programs like the heavy-lift helicopter.

Europe's Airbus AIR.PA is also challenging the ministry's plans, arguing that German firms should get a big share of the maintenance and management of the project.

The ministry has pushed back, saying it would be too unwieldy to award separate contracts for production and sustainment of the planes.

A top general with the Israeli Air Force, which is also considering buying the new helicopters, flew the aircraft during a 90-minute orientation flight at a Maryland air base on Nov. 7, a Navy spokesman said on Wednesday.

Brigadier General Nir Nin-Nun, commander of the Israeli Air Force’s air support and helicopter division, was the first international ally to fly the new helicopter, the Navy said.

“Flights like this give us an opportunity to strengthen relationships with our allies while sharing a taste of America’s next-generation heavy lift helicopter,” said CH-53K program manager U.S. Marine Corps Colonel Hank Vanderborght.

Israel is considering buying 20 of the helicopters, while Germany could buy around 40 aircraft.

Bringing the CH-53K helicopter to Berlin will allow military officials to compare the two aircraft on site. The Navy supports Sikorsky’s effort to bring an aircraft to the Berlin air show, a spokesman said.

Two Boeing CH-47 Chinook helicopters came to a conference in Germany in July, but the Lockheed aircraft, just entering production for the U.S. Marine Corps, was not on site.

Eight other NATO countries already use the CH-47, while Germany currently flies the CH-53G, an older version of the CH-53K that Lockheed will offer.

Some German military officials favor the CH-47 which they say is combat-proven and cheaper, but others say the larger CH-53K would allow growth in future missions.

The U.S. Marine Corps expects to declare the CH-53K ready for combat use in 2019. The Marines have said the average cost of the huge aircraft will be around $88 million per aircraft. The cost could drop somewhat if Germany, Israel and Japan also buy the planes.

Germany is hoping to start buying planes in 2023, about a year before that average cost will be achieved.

Experts say it would cost less for Germany to buy the Chinook, but that helicopter will require several upgrades in coming years that could add cost. It also carries less, so it takes more flights to accomplish the same mission.

Beth Parcella, in charge of Lockheed’s drive to win the German contract for the CH-53K, told Reuters she thought the helicopter still had good chances in the German competition.

“The price differential is not going to be anywhere as significant as it’s being portrayed,” she said. “It’s a larger, heavier aircraft, so it’s going to cost more. But it’s going to be a lot closer than people think.”

She said the new aircraft would also cost far less to service given its on-board diagnostic system.