Union Pacific and Norfolk Southern could announce a tentative merger agreement as early as this week, according to a published report. Bloomberg cited sources familiar with the talks in its report on Friday.

Union Pacific , the largest U.S. railroad operator, could reach an agreement to acquire rival Norfolk Southern as soon as early next week, Bloomberg News reported on Friday, citing people familiar with the matter.

Union Pacific Corp., North America’s largest railroad, is in advanced discussions with Norfolk Southern Corp. about a potential tie-up in what would be the industry’s largest deal ever.