Message : Required fields BRUSSELS (Reuters) - Insurance broker Aon's offer to sell assets in five EU countries and takeover target Willis Towers Watson's reinsurance arm may not be enough to address EU competition concerns, people familiar with the matter said on Tuesday. Aon is looking to the acquisition to create the world's largest insurance broker ahead of Marsh & McLennan Companies Inc as the industry grapples with rising claims and new challenges from the COVID-19 pandemic and climate change. Last Friday, the London-headquartered company submitted concessions to the European Union's competition watchdog, which did not disclose details in line with its policy. The watchdog often requires acquiring companies to make concessions that will strengthen rivals before giving its go-ahead.