Aug 2 (Reuters) - Warren Buffett's Berkshire Hathaway (BRKa.N) said on Saturday it took a $3.76 billion write-down on its stake in Kraft Heinz (KHC.O) during the second quarter, an acknowledgment the decade-old investment hasn't worked out.

Berkshire said the 12 per cent quarterly decline in insurance underwriting profit stemmed primarily from reinsurance businesses and some smaller insurance businesses. Geico, its best-known insurance business, saw pre-tax underwriting profit rise 2 per cent, as a 5 per cent increase in premiums offset a smaller rise in accident losses.

WARREN Buffett’s Berkshire Hathaway said on Saturday it took a $3.76 billion write-down on its stake in Kraft Heinz during the second quarter, an acknowledgment the decade-old investment hasn’t worked out.