Canadian Pacific Railway’s attempt to takeover Norfolk Southern Railway has already raised alarm with a group of Illinois lawmakers and prompted a pointed response from the Canada railroad.

Sen. Dick Durbin, D-Ill., on Dec. 14 urged the U.S. Surface Transportation Board, the rail regulatory agency, to consider the potential negative impact of the Canada railroad’s now $45 billion takeover bid on the nation’s historic rail chokepoint in Chicago. CP’s response to the letter, which was signed by the nine Democratic members of the Illinois Congressional Delegation, comes as the railroad inches closer to an outright proxy fight for control of NS after the Virginia-based railroad spurned takeover bids.

“Improving Chicago is a key objective of this transaction and one of the many ways it is in the public interest,” CP CEO E. Hunter Harrison wrote in a Thursday letter to Durbin and the delegation, “You can fully expect that this will be a major component of a compelling case to the STB.”

More at the Journal of Commerce