Factory automation maker Emerson Electric on Tuesday withdrew its offer to buy Rockwell Automation after the smaller rival rebuffed its buyout offer twice.

"We are disappointed that the Rockwell board refused even to discuss the potential combination of our two great companies," Emerson Chief Executive David Farr said in a statement.

Shares of Rockwell slipped 2 percent in pre-market trade. Emerson shares were up 1 percent.

Emerson said it plans to speed up the rate of repurchases over the next month and buy back up to $1 billion over the next 12 months.

Last week, Emerson sweetened its bid for Rockwell to $29 billion, which Rockwell rebuffed in its strongest rebuttal of the proposed combination of two of the world's largest factory equipment makers.

Rockwell has resisted Emerson's overtures not just because of disagreements over price, but also because it has argued that the combined company's industrial customers would be worse off because its products would no longer be available on a single platform and in one software environment.

In October, Rockwell rejected Emerson Electric's first offer for more than $27 billion, arguing that it undervalued the company.