Google's advertising crisis went global after some of the biggest marketers including AT&T and Johnson & Johnson halted spending on YouTube and the internet company's display network, citing concern their ads would run alongside offensive videos.

The controversy erupted last week after the London-based Times newspaper reported that some ads were running with YouTube videos that promoted terrorism or anti-Semitism.

The British government and the Guardian newspaper took down ads from the video site and Havas, the world's sixth-largest advertising and marketing company, pulled its British clients' ads from Google's display ad network and YouTube.

On Wednesday, the boycott spread across the Atlantic as US companies that are among the heaviest ad spenders pulled back, potentially costing Google and YouTube hundreds of millions of dollars in lost business.