ATLANTA, GA — Union Pacific is exploring an acquisition of Atlanta-based Norfolk Southern.

This could be the largest railroad deal ever merging the No. 1 and No. 5 North American railroads by revenue with a combined market value of almost $200B.

A deal would join Union Pacific’s network across the western US with Norfolk’s East Coast routes.

It would also create intense competitive pressure on rivals CSX and Berkshire Hathaway’s BNSF.

The sources say talks are at an early stage and there’s no guarantee of a deal. Representatives for both declined to comment.