The co-chief of Germany's ruling Social Democrats (SPD) is sceptical about NATO's goal for each member to spend 2% of economic output on defence, according to a newspaper report, underscoring ambivalence in the country about bolstering the military.
Saskia Esken told the Frankfurter Allgemeine Zeitung (FAZ) she had always wondered whether this calculation was "the right way".
The SPD has traditionally been more pacifist than most other mainstream parties in Germany, which long neglected its military in part due to guilt over its bloody 20th century past.
The party of Chancellor Olaf Scholz did recently commit to the 2% NATO goal, but as with junior coalition partner the Greens, has members who remain unconvinced.
According to FAZ, Esken expressed scepticism about the efforts of Defence Minister Boris Pistorius, also of the SPD, to hike defence spending in next year's budget.
"Ten billion euros (more) is a lot of money," she was quoted as saying.
Germany's regular 2023 defence budget was around 50 billion euros ($53.5 billion), well short of 75 billion euros, or 2% of economic output.
Scholz did announce a 100 billion euro special fund to revamp the military a year ago, days into Russia's invasion of Ukraine.
But some defence experts say that relying solely on this fund to reach the NATO target, and not raising the regular budget, would mean that once it is used up the government would struggle to get spending up to where it needed to be.
($1 = 0.9351 euros)
(Reporting by Scott Stevenson; Writing by Sarah Marsh; Editing by David Holmes)