EU antitrust regulators are asking Aon rivals and customers who is the best buyer for assets the insurance broker has offered to sell to address competition concerns about its $30 billion Willis Towers Watson bid, people familiar with the matter said.

Earlier this month, Aon offered to sell assets in five European Union countries, Willis’ reinsurance arm and its German retirement benefits and consulting business, people with direct knowledge of the matter had told Reuters.

The package of concessions to the European Commission also included Willis’ insurance broking activities in France, including French unit Gras Savoye, as well as in Germany, Spain and the Netherlands.

Aon is also prepared to sell Willis’ entire property and casualty business portfolio servicing large multinationals in those four countries and other European assets to service these clients, as well as its financial and professional lines.

The EU competition watchdog subsequently sought feedback from competitors and customers.

A questionnaire sent to them asked which nine rivals — French companies Besse, Siaci and Verspieren, German broker Funk, U.S. groups Gallagher and Lockton, and UK rivals Howden, McGill and BGC/Corant — would be a suitable buyer of Willis assets, one of the people said.

Gallagher said it does not comment on market speculation. There was no immediate response from the other companies to a Reuters request for comment.

EU regulators want to know if the prospective buyer should have certain traits like a multinational network that makes them better able to serve large multinational clients, the person said.

The EU competition enforcer typically prefers acquiring companies to sell assets to boost a rival, giving customers more choice.

The Commission is scheduled to decide by July 27 whether to clear or block the deal.