The FBI has told Scotland Yard it is "prepared to step in" if the Metropolitan Police fails to investigate the full extent of impropriety in the Murdoch empire.
The warning came at a meeting between the transatlantic law enforcement groups at the Ministry of Justice in London.
Every piece of evidence surrendered by News Corporation to Scotland Yard is also being passed to US investigators. The disclosures, which prompted more than 20 arrests, including 'Sun' journalists, have sparked a separate FBI inquiry into whether News Corporation bribed officials in Russia.
US investigators are also collecting evidence given to the Leveson Inquiry and parliamentary select committees.
"The FBI made it perfectly clear that if the British police drop the ball on this it will pick it up and run with it," said one legal source familiar with the US investigation.
Fear of such a US investigation, where financial penalties and potential jail sentences are more punitive than in the UK, is one reason cited why News Corporation, Mr Murdoch's US holding company, has stepped up efforts to assist UK police in recent months.
It is believed to be one of the reasons it handed over a cache of millions of emails containing evidence of possible crimes.
The Murdoch operation has assembled a team of US legal "big guns" to deal with inquiries by the FBI.
It is reported the FBI has found no evidence of phone hacking in the US so it is focusing on potential breaches of the Foreign Corrupt Practices Act (FCPA) designed to stop US-based firms bribing officials overseas.
News Corporation executives could be vulnerable if evidence exists that they demonstrated "wilful blindness" by failing to question wrongdoing.
James Murdoch, former chairman of News International, which oversees the scandal-hit newspapers, stood down from the board of Sotheby's, the auctioneer, last Friday. He resigned from the GlaxoSmithKline board in January and quit as chairman of News International last month.
James Murdoch denied knowing about phone hacking at the now defunct 'News of the World', though senior executives have called this into question.
Former 'Times' editor Harry Evans yesterday told BBC radio that Rupert Murdoch should be deprived of his ownership of 'The Times'.
Mr Evans, who resigned his editorship after disagreements with Mr Murdoch, launched an outspoken attack on his ownership.
He said that phone hacking, bribery and corruption was the penalty Britain had paid because "the leadership of the country is so in hock to a press proprietor who is given whatever he wants -- which is what they were going to do with BSkyB." (© Independent News Service)