WASHINGTON — While the British are already overwhelmed by the media frenzy surrounding Prince William's wedding, coverage in the United States is just now heating up and will reach fever pitch in the week before the April 29 ceremony at Westminster Abbey.

"It's catching on pretty quickly in the US. There is a fascination and the degree of media coverage is really starting to pick up now on the networks," said Diane Hall, president of 2 For Life Media, a Canadian company that launched an iPad application for the royal wedding.

"The amount of investment by the networks is significant."

The marriage of Prince William, second-in-line to the throne, to longtime girlfriend Kate Middleton is expected to attract 2.5 billion television viewers from around the world -- more than two-and-a-half times the audience of the marriage of William's parents Prince Charles and the late Princess Diana, in 1981.

American television networks and cable channels plan to move their headquarters to the banks of the River Thames a week before the big day.

The NBC network and its cable affiliate MSNBC plan 20 hours of coverage on the day of the wedding, with a dozen of their journalists and personalities on the ground.

Cable channels including Bravo and E! will feature documentaries like "Inside the Royal Wedding" and will grade the royal styles with "Fashion Police" segments.

The original 24/7 cable news network CNN is dispatching 50 of its staff including top stars Anderson Cooper and Piers Morgan, who replaced Larry King, to London, it told AFP.

CNN will begin its wedding day coverage at 4H00 in the morning in the United States.

In the days before the wedding, CNN will premiere a documentary dedicated to the future princess, entitled "The Woman Who Would be Queen". The piece focuses on Middleton's life and looks at the origins of the romance from their university days at St. Andrews in Scotland.

But with the exploding popularity of microblogging, social media and digital applications -- nearly every media outlet has a royal wedding app -- the wedding is the perfect multimedia event.

"It's a great story, a good news event," Hall said. "The big change is social media, you can watch it when you want. At the end of the day, people want to comment on it."

Media outlets from Yahoo to NBC have Facebook pages dedicated the the royal couple.

"The comments that get posted on our Facebook wall show such a real fondness for William because of Diana, it's incredible," Hall said.

On 2 For Life's royal wedding Facebook page, which has attracted 12,000 fans, people have posted messages including: "Diana would be so proud of him" and "It's sad Diana won't be there."

Applications for iPad and soon iPhone are flourishing. NBC's "Royal Wedding App" has 300 photos, an interactive royal family tree, and advice to create your own viewing party. Other apps like "Royal Wedding 2011" discuss royal protocol and propose wedding dress choices for Kate.