Aon’s profit fell 1% to $US809 million ($1.1 billion) in the September quarter, as higher operating expenses offset an increase in revenue.

Profit for the nine months to September gained 4% to $US13.38 billion ($18.9 billion).

Total revenue for the quarter was up 3% to $US4.1 billion ($5.8 billion), but the operating expense rose 3% to $US3.3 billion ($4.7 billion) due to investment in technology and costs such as reducing staff numbers.

CEO Greg Case says the broker is investing in AI-enabled analytics, innovative capabilities and capital solutions.

Aon expects to close its $US17 billion ($24 billion) acquisition of US mid-market broker USI Insurance Services in the final quarter.

The acquisition will be debt-funded, and Aon says it will prioritise repayments.