Charles Dharapak, Associated Press
President Barack Obama listens as British Prime Minister David Cameron speaks during a news conference at the G7 summit in Brussels, Belgium, Thursday, June 5, 2014.

BRUSSELS — President Barack Obama said Thursday that it's hard to see how Britain would benefit by leaving the European Union given that the 28-nation bloc's decisions "have an enormous impact on its economic and political life."

Britain must make its own choice, Obama said, but insisted that it is always an asset for the United States to know one of its closest allies "has a seat at the table in the larger European project."

Obama spoke at a joint news conference with British Prime Minister David Cameron in Brussels after the G-7 summit of major economies.

Britain's Conservative-led government is increasingly skeptical of what it perceives as meddling by the EU in national matters and has promised to hold a referendum on whether Britain should exit the EU, a political and economic bloc with half a billion citizens.

Britain's fraught relationship with the EU is what many observers call the most vexing issue on Cameron's agenda. He is pushing for a reform of the EU that would restore more power to national authorities.

"It's about making some significant changes and then putting that decision in a referendum to the British people, but very much recommending that we stay in a reformed European Union," Cameron said.

So far, however, Britain has mustered only a few allies across Europe.

In elections for the European Parliament last month, the eurosceptic UKIP party came in first in Britain, further fueling the debate on Europe. Many of Cameron's fellow Tories would love to turn their back on the EU sooner than later.

Yet Britain's business lobbies have warned leaving the EU would weaken the country's economy and put Britain at risk of being shut out from a powerful political bloc and the world's biggest free-trade zone.

"And it's hard for me to imagine that project going well in the absence of Great Britain," Obama said. "And I think it's also hard for me to imagine that it would be advantageous for Great Britain to be excluded from political decisions that have an enormous impact on its economic and political life."

In addition, Britain is rattled by Scotland seeking its independence, on which a referendum will be held in September.

When asked about the possibility of Scotland leaving the United Kingdom, Obama said "we obviously have a deep interest in making sure that one of the closest allies that we will ever have remains a strong, robust, united and effective partner."

Obama avoided taking sides by saying it is for the Scots themselves to decide, but added "from the outside, at least, it looks like things have worked pretty well" so far with Scotland being part of the United Kingdom.

And in light of Friday's D-Day celebrations in France, Obama said it was the steadfastness of Great Britain that, in part, allows world leaders to be in Brussels, the seat "of a unified and extraordinarily prosperous Europe."

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