CSX Corp. stock is up on reports that Union Pacific is interested in buying the Jacksonville-headquartered railroad company. CSX Corp.’s stock rose to its highest level of the year July 17 after a report that Union Pacific Corp. is seeking to buy one of the two major eastern railroads, CSX or Norfolk Southern Corp.

Union Pacific is working with Morgan Stanley investment bankers to provide guidance on the potential acquisition of another Class I railroad, the online publication Semafor reported on Wednesday, citing people familiar with the matter.

Shares of freight transportation company Union Pacific (NYSE:UNP) fell 3.2% in the pre-market session after reports revealed the company was considering a major acquisition of an East Coast railroad.

BNSF Railway and Union Pacific ( NYSE: UNP) have networks that connect the West Coast to the central and Midwest regions but do not, by themselves, offer uninterrupted coast-to-coast coverage. Meanwhile,

Union Pacific appears to be using a familiar playbook that large, publicly traded companies trot out when considering mergers and acquisitions: Send up trial balloons and see how they fly. These trial balloons let management gauge market reaction,

Berkshire might see a bid for CSX as a defensive maneuver if its chief rival, Union Pacific, seeks to create a transcontinental railroad.