The move underscores Berkshire’s growing ambitions in Japan, where around six years ago — under the leadership of Warren Buffett — it revealed it had invested in the country’s largest trading houses. Buffett said in an annual letter to shareholders that the firm was looking to raise ownership in Japan’s five largest trading houses “over time.”

The latest deal shows Berkshire is eager to win a slice of Japan’s thriving insurance business, an increasingly attractive market for foreign firms. KKR & Co., Apollo Global Management Inc. and other big international players have made moves to expand in the life insurance sector, joining a rush among foreign firms to tap rising opportunities in Japan.

“The partnership with Berkshire is likely to provide an advantage by leveraging global expertise to expand the scope of operations ahead of others,” said Ikuo Mitsui, a fund manager at Aizawa Securities Co.

Tokio Marine is Japan’s largest property and casualty insurance company.

The deal means that Tokio Marine can use National Indemnity as an option for reinsurance without restriction on the type of insurance, said spokesman Mitsuhiro Izu, adding that the initiative for the partnership came from Berkshire’s side.

The partnership will last for a decade, and in the first five years both Berkshire and Tokio Marine will not be able to enter into similar agreements with competitors, Izu added.

Berkshire will buy around $1.8 billion of treasury stock held by Tokio Marine, which the Japanese firm will then match by buying back the same amount of existing shares. If Berkshire buys any more of the firm’s stock, it is likely to do so in the open market, Tokio Marine said in its statement.

The US firm said it will not raise its stake above 9.9% without approval from Tokio Marine’s board.