Germany has expressed serious concerns about the completion of the purchase of US F-35 fighter jets as part of a plan to modernize its military forces, according to a "secret message" obtained by Agence France-Presse.

Last March

, Berlin announced

its intention to purchase 35 warplanes manufactured by the American company "Lockheed Martin" to replace its aging fleet of "Tornado" aircraft.

But the German Ministry of Defense has raised concerns about "delay" factors and "additional costs" impeding the deal worth about 10 billion euros, according to a "confidential" letter addressed to the Parliament's Budget Committee.

The letter referred to risks related to the completion of the development of the air base that will host F-35 fighters, in addition to security requirements and difficulties in obtaining approvals to fly aircraft in Germany at the required time.

A spokesman for the Ministry of Defense said there would be "close cooperation" with parliament and "clarification" of matters.

Parliamentary sources told Agence France-Presse that an emergency meeting will be held on Monday at the Ministry of Defense, attended by members of the budget committee from the three parties in the ruling coalition in Germany.

The committee is supposed to release the first batch of the deal's money on December 14.

German Chancellor Olaf Scholz (centre) in front of an F-35 fighter of the Italian Air Force during the Berlin Airshow (Reuters)

Document prepared by the Ministry of Finance

The document, seen by Agence France-Presse, was prepared by the Ministry of Finance for the committee, and was based on assessments by the Ministry of Defense.

According to the document, there are doubts surrounding the completion of the necessary updates for the Buchel Air Force Base, which will receive aircraft by 2026, once the delivery process begins.

It warned that the current timeframe was "very ambitious" and that complex security requirements from the US side could lead to further delays and cost increases.

She added that there is also a risk that approvals for F-35 fighter flight operations in Germany could not be obtained on time due to the lack of "required documents".

The document also pointed to other factors that could lead to higher costs, including inflation, fluctuations in the exchange rate between the dollar and the euro, and high production costs.

Funding for the deal comes from a €100 billion plan for the armed forces unveiled in the aftermath of the Russia-Ukraine war in an effort to modernize the German military.

German Chancellor Olaf Scholz said last week that he wanted to complete the deal for the world's newest F-35 jets by the end of the year.