Frankfurt will almost certainly move on Thursday.
Market odds put a quarter-point hike at close to certainty, which would lift the European Central Bank's deposit rate from 2.25% to 2.5%.
What makes this a difficult call is not whether the ECB acts, but why, and whether the reasoning survives contact with the data.
The path here has been compressed as the ECB raised rates on 11 June for the first time in three years, lifting the deposit rate from 2% to 2.25% in response to the energy shock from the Iran war, and then held rates in July while Christine Lagarde pointed hawkishly towards September.
August's inflation figures removed any remaining doubt with eurozone inflation hitting 3.3%, up from 2.9% in July and the highest since September 2023, as energy inflation surged to 14.3% from 10.3%.
