Willis Group Holdings Plc, the third-largest insurance broker, offered to buy the 70 percent of Gras Savoye that it doesn’t already own to expand in France, Eastern Europe and the Middle East.

Willis will pay 550 million euros ($590 million), a sum that includes the repayment of outstanding third-party debt, the London-based buyer said Wednesday in a statement.

Chief Executive Officer Dominic Casserley has been pursuing acquisitions to extend Willis’s geographic reach and add customers seeking coverage for specialized risks. Willis announced a deal in January to buy Miller Insurance Services to work with clients in industries including shipping, construction and energy. Casserley added the Max Matthiessen business last year to bolster operations in the Nordic region.

“The combination of Miller and Gras Savoye is an important change in our overall footprint,” Casserley said in an interview. “We’ve always wanted to be around the world. We’ve made the investment in Gras Savoye with that in mind.”

Gras Savoye is France’s largest broker, Willis said. The Paris-based company is in the fifth-largest insurance brokerage market and will also help Willis reach fast-growing regions like Africa, Casserley said.

“The board of Gras Savoye is delighted to receive the offer,” Patrick Lucas, Gras Savoye chairman, said in the statement. “We have worked together for 40 years, and this offer is the logical next step in that relationship.”

The acquisition will give Willis almost 4,000 new employees, adding to the 18,000 it already had. The deal is subject to regulatory and shareholder approval, Willis said, and is expected to close by the end of the year. It could boost earnings by 2018.