David Cameron will hold talks with Barack Obama today to highlight the benefits for Britain of a free trade deal between the EU and the US.
The Prime Minister will argue that an agreement could be worth up to £10 billion a year to the economy.
Mr Cameron may also need to reassure the president about the UK's future within the grouping.
It comes as Cabinet ministers Michael Gove and Philip Hammond yesterday became the latest senior figures to indicate they would currently vote to leave the EU.
More top news
A hacker group who claimed to be behind a cyber attack on Sony Pictures have posted a message online apparently mocking the FBI.
The returns of Benedict Cumberbatch's detective and the X Factor judge were among 2014's most tweeted TV moments in a billion conversations.
A family has issued an appeal to help find their missing pet turkey - in case he gets gobbled up as someone's Christmas dinner.