Arthur J. Gallagher will buy Willis Towers Watson (WTW) treaty reinsurance broking operations for $US3.25 billion ($4.4 billion), reviving an acquisition initially flagged before the collapse of Aon’s proposed takeover of WTW.

The deal includes the potential additional payment of $US750 million ($1 billion) subject to certain third-year revenue targets.

Aon and WTW said in May that they planned to sell the Willis Re reinsurance business and certain UK, European and North American operations to Gallagher as part of efforts to win regulatory clearance for their merger.

The asset sales didn’t allay US Justice Department concerns and the merger deal to create the world’s largest broker was dropped, but Gallagher has continued to pursue its opportunity.

“Broadening our reinsurance brokerage offerings has been a strategic objective at Gallagher and this acquisition will significantly enhance our global value proposition,” CEO Patrick Gallagher said.

“We were very impressed with the Willis Towers Watson reinsurance professionals we met during our initial due diligence and strongly believe a combination will significantly enhance our offerings to clients and prospects.”

The acquisition includes all of Willis Re’s treaty reinsurance broking business, which last year generated an estimated $US745 million ($1 billion) of pro-forma revenue.

The business operates in 24 countries, places over $US10 billion ($13.5 billion) of premium annually, represents over 750 insurance and reinsurance company clients and has 2200 employees.

Gallagher expects the deal to close in the fourth quarter of this year, subject to regulatory approvals.