BRUSSELS (Reuters) - Aon’s $30 billion bid for Willis Towers Watson to create the world’s largest insurance broker faces a five-month long investigation after EU antitrust regulators voiced concerns that the deal may hurt competition in key markets. The merger of the world’s second and third largest brokers would overtake world No. 1 Marsh & McLennan Companies Inc. The deal came just as financial markets were sliding as a result of the COVID-19 crisis. The pandemic has triggered a sharp rise in claims for insurers, on top of other challenges such as climate change, and hit their investment portfolios. Falling valuations and companies looking to shore up business models have in turn sparked a run of deals across the insurance industry. Aon said it was confident of securing EU approval without having to sell any assets to allay competition concerns and that it was on track to close the deal in the first half of 2021. The European Commission said the deal could significantly reduce competition in markets for commercial risk brokerage services, re-insurance brokerage and provision of retirement and health & welfare services to commercial customers. It cited brokerage services to large multi-national customers in property and casualty, financial and professional, credit and political risk, cyber and marine as well as customers in the space and aerospace manufacturing industry as the most affected. The EU investigation will also examine the provision of reinsurance brokerage services and the provision of retirement and health & welfare services. The EU competition enforcer set a May 10 date for its decision. Reuters had reported on Dec. 15 that the EU competition enforcer would open an in-depth investigation into the deal after Aon declined to offer concessions to address EU competition concerns.