ST. LOUIS (AP) -- Food maker Ralcorp Holdings Inc. said Monday it has agreed to buy American Italian Pasta Co. for about $1.2 billion and has acquired two cracker makers.

But the maker of Post cereals and a variety of foods sold under store labels also offered guidance for its fiscal third quarter below Wall Street expectations due to tough competition in the cereal category.

Its shares fell $3.47, or 5.6 percent, to $58.70 in premarket trading.

Ralcorp said it will pay $53 per share for American Italian Pasta Co., a 27 percent premium over the Kansas City pasta maker's closing price of $41.73 on Friday.

American Italian Pasta shares rose $10.92, or 26.2 percent, to $52.65 on premarket trading.

The St. Louis food maker also said it acquired North American Baking Ltd., a Canadian maker of private-label specialty crackers, and J.T. Bakeries, which also makes crackers, for undisclosed terms.

Ralcorp expects the cracker deals to be "slightly" beneficial to earnings for the rest of the year.

Meanwhile, Ralcorp forecast a drop in its fiscal third-quarter net income to $1 a share, down $1.31 per share in the prior year. Analysts expect earnings of $1.29 per share, according to a survey by Thomson Reuters. They typically exclude one-time items from their estimates.

The company said lower returns on markdowns at its Post Foods unit and branded competition for its private-label cereal hurt results at its Ralston Foods segment.

Ralcorp said it doesn't plan to give guidance again except in unique circumstances.

The deal for American Italian Pasta is expected to close during Ralcorp's fiscal fourth-quarter ending Sept. 30.

Ralcorp will fund the deal through a cash on hand, existing credit facilities and a bridge facility that it has received a commitment letter for, or other debt or equity arrangements.

Ralcorp said it expects the deal to help earnings by at least 50 cents per share, excluding one-time items, in 2010.