EU competition authorities have approved Aon’s $30bn takeover of Willis Towers Watson, a deal designed to create the world’s biggest insurance broker but one that is facing investigation by US regulators.

The European Commission said on Friday it had accepted a package of remedies offered by the two sides, the bulk of which came in a $3.6bn deal struck in May to offload a series of businesses to rival Gallagher. Aon has also offered to sell its German retirement consulting and investment solutions businesses to a “suitable purchaser”.

The commission’s competition chief Margrethe Vestager said the package of disposals “ensures that European companies, including insurance companies and large multinational customers, will continue to have a good choice and good services when selecting a broker suitable for their needs”.

Aon and Willis said that securing approval in Brussels was “a major step that demonstrates continued progress toward obtaining regulatory clearances for the proposed combination”.

In a joint statement, they added: “Both firms operate across broad, competitive areas of the economy and believe this approval affirms that our proposed combination will accelerate innovation on behalf of clients, creating more choice in an already dynamic and competitive marketplace.”

But the deal has a tougher path to completion in the US, the two companies’ other major market.

The Department of Justice last month sued to block the takeover, saying that the combination of two of the big three insurance brokers would “eliminate substantial head-to-head competition and likely lead to higher prices and less innovation, harming American businesses and their customers, employees, and retirees”.

Aon and Willis had been hoping to close the deal in the third quarter — a completion timetable that had already slipped from the first half of the year as regulatory probes dragged on.

In a US court hearing earlier this week, the brokers pushed for a September start date to the antitrust trial, while a representative for the government argued for it to kick off in January to allow for preparation time.

In the end, the two sides agreed to get under way on November 18, but US district judge Reggie Walton warned that there was a risk that even this date would be pushed back because a number of cases had been assigned to him relating to the storming of the US capitol in January.

The deal is one of the very few complex merger probes that come to a conclusion in Brussels in recent months, following a spike in mergers and acquisitions activity during the pandemic.

A merger between Nvidia and Arm — expected to be filed at some point later this year — is set to receive deep scrutiny from regulators over competition concerns.