Emerson raised its bid to $225 per share, valuing Rockwell at $29 billion. Rockwell rejected Emerson's $215 a share bid last month. Rockwell shares finished Thursday's session up 2.6 percent at $193.61.
"The industrial logic for this combination is clear. A combination of Emerson and Rockwell would create a leader in the $200 billion global automation market," Emerson CEO David Farr said in a letter to Rockwell CEO Blake Moret. "The combination of Emerson and Rockwell would accelerate our combined growth and position us for success for many years to come."
Emerson has made multiple offers to acquire the automation company. Shares of Rockwell — which provides industrial automation power, control and information solutions to manufacturers — closed at $188.73 on Wednesday and have risen more than 40 percent in 2017.
Rockwell Automation confirmed in a separate release that it had received Emerson's bid. Rockwell said its board of directors "will carefully review Emerson's proposal to determine the course of action that it believes is in the best interest of the Company."