On Wednesday, Comcast confirmed that it was preparing a higher, all-cash offer for most of the media assets of Twenty-First Century Fox, setting up a bidding war with rival Walt Disney. The largest U.S. cable operator said it was in advanced stages of readying a bid that would be superior to Disney’s all-stock offer. By going public with its plans, Comcast is putting pressure on Fox and its shareholders to not rush into approving the Disney deal.