EU-US trade deal

But it is the prospect of an EU-US trade deal and the lucrative dividends that such an agreement could bring both countries that Cameron was keen to stress before the trip even as one of his own government ministers said he thought Britain should leave the EU.  

In particular, he is hoping Obama will help him clinch an agreement to start talks on such a trade deal in the margins of the G8 summit, an achievement he believes would give the global economy a shot in the arm at a time when his own country and many others are seeing only a fragile economic recovery.

Britain's Prime Minister David Cameron speaks at the Global Investment Conference 2013 in London, May 9, 2013. Cameron took on critics in his own Conservative party on Thursday, saying it would be wrong for Britain to leave the European Union.[Photo/Agencies]

"Britain and America can once again lead the way in meeting the greatest challenge of our time: securing the growth and stability on which the prosperity of the whole world depends," Cameron wrote in an article for the Wall Street Journal.

He said an EU-US trade deal would boost the British economy by 10 billion pounds a year and the US economy by 63 billion pounds annually.

"When times are tough, some want to put the barriers up, to look inwards, and to protect themselves from the world. But Britain and America stand for a better way," he wrote in the same article.

Cameron is hoping Obama will also help him turn high-flown rhetoric on cracking down on global tax evasion into a meaningful international agreement at the G8 summit.    

"We must fight the scourge of tax evasion by promoting a new global standard for automatic information exchange between tax authorities," Cameron said.

Using some of his strongest language on the subject yet, he added: "We must lift the veil of secrecy that too often lets corrupt corporations and officials in some countries run rings around the law."

A global standard for resource-extracting companies that obliged them to report all payments to governments across the world would be also be an important step forward, he said.