Insurance and reinsurance broker Aon and Manchester United have signed a deal that will extend their relationship by an additional eight-years.The sponsorship deal, worth an estimated $240 million, will see Aon’s logo on United’s training uniform through 2021, while the club’s Carrington training ground will be renamed the Aon Training Complex starting July 1.A key tenet of Aon's sponsorship will be the endorsement of United's pre-season tours, which often visit parts of Asia and Africa to tap into a rapidly growing fan base.United, which last year floated on the New York Stock Exchange and has been stacking up sponsorship deals in recent months, bought back its training uniform sponsorship rights from Deutche Post AG (DPW)’s DHL, which was in the middle of a four-year, £40 million contract.In August, Aon enters the final season of a four-year, $122.7 million contract as sponsors of United’s main game jerseys. The insurer will be replaced by General Motors Co.’s (GM) Chevrolet brand at the start of the 2014-15 season. The carmaker is paying $559 million over seven seasons.United also holds deals with Nike Inc., online gaming firm Bwin. Party and Indian beer brand Singha.United sits 12 points clear at the top of the English Premier League as it seeks a 20th Premier League championship.