BERLIN, Oct 20 (Reuters) - German Defence Minister Boris

Pistorius intends to order an additional 15 F-35 fighter jets

from U.S. manufacturer Lockheed Martin ( LMT ), a parliamentary

source told Reuters on Monday, backing a report by Spiegel

magazine.

Planners expect the additional aircraft to cost some 2.5

billion euros ($2.9 billion) according to confidential documents

prepared for parliament's budget committee, the source said.

Germany has already ordered 35 of the U.S.-made jets to

replace its fleet of 85 ageing Tornado fighter jets, which are

set to be decommissioned.

The F-35 aircraft are designated to succeed the Tornados in

their role of carrying U.S. nuclear bombs stored in Germany in

the event of a conflict.

Berlin previously denied plans to acquire an additional 15

F-35 fighter jets in July, but a significantly expanded defence

budget has since created more scope for weapons purchases.

At the time, a

military source

told Reuters that the idea of acquiring 15 more F-35 jets

had been part of earlier discussions.

Any decision to purchase more F-35 aircraft could spark

fresh tensions between

Germany

and France who have been at odds over their struggling

fighter jet project

FCAS

, or SCAF in French.