Weston Hicks’s Alleghany Corp. will pay $400 million to wind down reinsurance deals with American International Group Inc. and Warren Buffett’s Berkshire Hathaway Inc. for policies that date back decades.

Transatlantic Reinsurance Co., owned by Hicks’s firm, will end contracts that covered asbestos-related illness and environmental liabilities, according to an Alleghany regulatory filing Tuesday. Alleghany will post a $20 million charge in the fourth quarter tied to the accord.

Transatlantic estimates that the latest accord “will eliminate approximately 90 percent of its liabilities for A&E losses occurring in 1986 and prior years,” Alleghany said in the filing, referring to asbestos and environmental claims.

AIG had sought in recent years to limit asbestos-related liabilities as costs from the policies climbed, and the insurer was pressured by regulators and investors to simplify the business. Buffett’s company, however, has been taking on such risks because the reinsurance deals add reserves that the billionaire can invest. Berkshire reached a deal in 2011 to receive $1.65 billion for taking on asbestos obligations from AIG.

Alleghany said the $400 million deal is with AIG Property Casualty Inc. and the National Indemnity and Resolute Management operations at Omaha, Nebraska-based Berkshire. The filing didn’t specify how the funds would be divided, and representatives of AIG and New York-based Alleghany declined to discuss the breakdown. Buffett didn’t immediately respond to a request for comment left with an assistant.

–With assistance from Noah Buhayar.