BERLIN (Reuters) - Pentagon officials briefed German military on the Lockheed Martin Corp F-35 fighter jet this week but Berlin said no procurement decisions have been taken.

A Lockheed Martin Corp F-35 stealth fighter jet lands at the Avalon Airshow in Victoria, Australia, March 3, 2017. Australian Defence Force/Handout via REUTERS

Germany, which is looking to replace its aging Tornado fighter jets, is due to decide in mid-2018 about whether to start a new fighter development program or buy an existing fighter.

A German Defence Ministry spokesman said the decision will hinge largely on assessments of how long the Tornados can stay in use.

“The F-35 is one of many options we are exploring,” the spokesman said.

Any move to buy a U.S. warplane could run into political resistance in Germany, which has strong labor unions, and given a big push by Europe to develop its own military equipment.

The German Air Force asked the U.S. military in May for a classified briefing on the F-35 fighter jet as part of an “in-depth evaluation of market available solutions.”

Germany’s interest in the F-35 took some European defense industry officials by surprise, given a big push by European aerospace giant Airbus and other European defense companies to develop a next-generation European fighter.

Lockheed, which is already building the F-35 fighter for several other NATO allies - the United States, Britain, Italy, Turkey, Norway, the Netherlands and Denmark - also plans to provide the German defense ministry with information about opportunities for German industry to participate in the F-35 program, a source familiar with the matter told Reuters.

This week’s briefings took place in Bonn, Germany, on Monday and Tuesday and involved a German one-star general, as well as working groups looking at specific weapons requirements and capabilities, according to another source briefed on the matter.

“This meeting is consistent with the standard Foreign Military Sales process where we explain the path to F-35 acquisition and provide a top-level F-35 capabilities brief,” F-35 program office spokesman Joe DellaVedova said.

The German military plans to send Washington a formal “letter of request” for information about the F-35 and Boeing Co’s F-15 and F/A-18E/F fighter jets later this summer, the ministry spokesman said.

It will also gather information from Airbus about its work on a next-generation weapons system, he added.

Experts also see the F-35 as the leading contender in a Belgian fighter competition that includes the Eurofighter Typhoon and the Dassault Aviation Rafale. Sweden’s SAAB and Boeing have withdrawn from that tender.