Buffett owned UnitedHealth shares before selling his stake in 2010, though his Berkshire Hathaway recently acquired shares.

The blue-chip Dow was on track to open at a record high on Friday, underpinned by expectations of an interest rate cut in September and gains in UnitedHealth's shares after Berkshire Hathaway raised its stake in the health insurer.

The blue-chip Dow opened at a record high on Friday, as UnitedHealth's shares jumped after Berkshire Hathaway raised its stake in the health insurer, while expectations of an