Aon’s proposed takeover of rival broker Willis Towers Watson has won the support of two key shareholder proxy advisory firms ahead of a vote next week.

Institutional Shareholder Services and Glass Lewis & Co have both completed independent reports supporting the deal, which will create the largest global insurance broker.

“We find the proposed merger is strategically and financially compelling and structured in a reasonable manner,” Glass Lewis notes.

A report by Institutional Shareholder Services says the rationale behind the merger is “sound”, and is expected to deliver $US800 million ($1.1 billion) in cost savings and will add to adjusted earnings per share and free up cashflow.

The two broking firms also have complementary businesses and client bases across geographies and client segments, which may offer revenue upside, according to its assessment.

Shareholders of both companies will meet on Wednesday next week to vote on the deal, paving the way for its completion in the first half of next year, subject to regulatory approvals.

The all-stock offer of 1.08 Aon shares for each Willis Towers Watson share was worth $US29.9 billion ($41.73 billion) when announced in March.

The new firm will operate under London-based Aon’s brand, and be led by Aon CEO Greg Case and CFO Christa Davies. Willis Towers Watson CEO John Haley will become Executive Chairman.