Fitch Ratings placed U.S. food company General Mills Inc. on negative watch due to its pending $8.0 billion acquisition of Blue Buffalo Pet Products Inc., which the debt watcher said would lead to increased leverage.

The rating agency said it was expecting General Mills to raise debt of about $6 billion to $6.5 billion to help fund the acquisition, which is set to close in May.

Fitch projected General Mills' pro forma leverage to rise to 4.2x on last-12-month EBITDA at the close of the transaction, from 2.8x in fiscal 2017.

Leverage would fall to the mid-3x range over the next two years, assuming that General Mills uses free cash flow to pay down debt, Fitch said.

Fitch expects to resolve the rating watch status after the final financing details of the deal are worked out, with a one-notch downgrade seen due to the higher leverage.

General Mills' long-term and short-term issuer default ratings are BBB+ and F2, respectively.

On Feb. 23, S&P Global Ratings and Moody's hit General Mills with downgrades due to the Blue Buffalo deal.

S&P Global Ratings and S&P Global Market Intelligence are owned by S&P Global Inc.