Germany confirmed Monday it aims to replace its ageing fleet of Tornado fighter-bombers with aircraft from both European manufacturer Airbus and US-based Boeing.

Berlin is eager to balance European and American alliances via its military aircraft-buying scheme, but the decision to move ahead with the US purchases has angered some politicians who allege a lack of transparency.

An official decision on the procurement plan will be sent to parliament's defence committee "in the coming days," defence ministry spokesman Arne Collatz-Johannsen told reporters in Berlin. "Fewer than a third" of the new aircraft would be American models, with the majority made up of European products, he added.

A source close to the plans confirmed German media reports that the defence ministry prefers to hedge its bets between EU and US suppliers, by purchasing around 90 Airbus-made Eurofighters and 45 Boeing F-18 jets.

A solution balancing allies on both sides of the Atlantic is seen by the conservative-led defence ministry as vital because even after the Tornados are retired, Berlin must maintain its air force's capability to carry American nuclear weapons as part of its commitments under the NATO military alliance.

At present, the Tornado is the only Luftwaffe, or air force, aircraft certified to carry the nuclear bombs. "We recommend a mixed solution which would keep the European defence ministry running at capacity and what's more, concerning less than a third of the total, possibly come from non-European suppliers," Collatz-Johannsen said.

Grumbling in the ranks

German Defence Minister Annegret Kramp-Karrenbauer had told her American counterpart Mark Esper about the plans over the weekend, the spokesman said. Der Spiegel magazine recently cited a German federal auditors' report describing the 1970s-era Tornado as a "weapons system that has become obsolete, increasingly marked by technical faults and lack of availability."

Collatz-Johannsen said operating the planes would "no longer be economical" by 2030, making 2025 the deadline for finding a replacement. Meanwhile a Franco-German next-generation fighter dubbed the Future Combat Air System (FCAS) is not expected to be ready until 2040. "That leaves us with a capability gap to bridge," the defence spokesman said.

But minister Kramp-Karrenbauer's decision to inform the US early -- a final procurement decision is unlikely before the next parliament beginning in 2021 -- has angered some from the the centre-left social democrats (SPD), junior coalition partners in Chancellor Angela Merkel's government.

"Nothing has been made transparent to us in any way," defence committee chief Wolfgang Hellmich told the Sueddeutsche Zeitung daily. "So far we have received nothing."

While the defence spokesman said SPD Finance Minister Olaf Scholz and Foreign Minister Heiko Maas had been informed, the centre-left party's most determined opponents of nuclear weapons -- and of buying American planes to carry them -- are among its MPs.