The Sears Tower is shown in the skyline of downtown Chicago March 29, 2008. REUTERS/Frank Polich

CHICAGO (Reuters) - The 110-story Sears Tower, tallest office building in the Western Hemisphere, will be renamed the Willis Tower, global insurance broker Willis Group Holdings said on Thursday.

Willis said it was leasing multiple floors in the 1,451-foot (442-meter) structure in downtown Chicago to consolidate offices. As part of the deal, it will become the Willis Tower this summer when the move takes place, the company said.

Sears, once the largest U.S. retailer, occupied what was then the world’s tallest building as its headquarters after the skyscraper was completed in 1973. But it moved out in the early 1990s.

Over the years the company lost ground to discounters like Wal-Mart Stores Inc in the clothing business and big-box hardware retailers like Home Depot Inc.

Today’s Sears Holdings Corp is controlled by billionaire financier Edward Lampert.

The Council on Tall Buildings and Urban Habitat lists the steel and glass tower as the fifth-tallest completed building in the world. The tallest, at 1,670 feet, is the Taipei 101 building in Taiwan’s capital.

Willis Group Holdings refers to itself as a global insurance broker “developing and delivering professional insurance, reinsurance, risk management, financial, and human resource consulting and actuarial services.”

It says it has more than 400 offices in nearly 120 countries.