By Andrew Osborn and Peter Griffiths
LONDON (Reuters) - An outspoken intervention by a senior U.S. official who said Britain should not leave the European Union opened up a new rift between Prime Minister David Cameron and his deputy on Thursday.
Cameron played down any suggestion of a disagreement with Washington over his country's membership of the EU, but Deputy Prime Minister Nick Clegg, his junior coalition partner, said U.S. concerns over Europe were spot on.
Both men were reacting after Philip H. Gordon, the U.S. assistant secretary of state for European and Eurasian Affairs, told a media briefing in London the previous day that Washington feared a British exit from the EU would run counter to U.S. interests.
Gordon's intervention, a rare and unusually strong diplomatic foray into an emotive domestic debate, made front page news in Britain where Cameron is preparing to deliver a speech setting out his plans to try to renegotiate the country's relationship with the EU and then put the deal to a vote.
Cameron faces a dilemma. Many MPs in his own ruling Conservative Party are pressuring him to call a fully-fledged referendum on whether Britain should remain in the EU, a demand backed by opinion polls which show a majority of Britons would, if given the chance, vote to leave the 27-nation bloc.
But business leaders in Britain have said they are strongly opposed to the prospect of the country radically downgrading ties with its biggest trading partner, while international partners from the United States to Germany and Ireland have made it clear they oppose a British EU exit or "Brixit" and think such a move would isolate and damage Britain itself.
Politicians on both sides of the Atlantic often refer to ties between Britain and the United States as the "special relationship", a phrase coined by former British prime minister Winston Churchill, whose own mother was American.
But in recent years some analysts and politicians have questioned how closely the United States listens to Britain and whether the days of a privileged alliance are in the past.
Asked on Thursday whether Gordon's comments that the United States wanted Britain to stay in the EU were appropriate, the response from the prime minister's official spokesman was dry.
"He was setting out his views," he said.
"What Philip Gordon was setting out yesterday was that the U.S. is strongly in favor of an outward-looking European Union with Britain in it and that is very much our view."
The defensive response contrasted with that of Clegg, the leader of the Liberal Democrat Party, the junior member of the two-party coalition government.
The two coalition members have clashed on everything from reform of the upper house of parliament to cuts in state handouts but have pledged to continue to govern together in the knowledge that they would lose an election to the opposition Labour party if such a vote was held today.
Clegg, who has derided Cameron's idea of repatriating some powers from the EU as "a false promise wrapped in a Union Jack", has made clear his party does not want to see Britain distance itself from the EU at all.
"In one sense it's entirely unsurprising," he said of Gordon's comments. "Americans have been saying for generations now, for ages, since the 1950s, that Britain and the special relationship between Britain and America … is one that is partly based on the fact that we are valuable to our American friends," Clegg told LBC radio.
"They are perfectly entitled to say ‘look if you're interested in the American perspective, we think Britain stands taller in the world if you stand tall in your own neck of the woods'."
Tim Bale, a politics professor at the University of London told Reuters that pressure was building on Cameron to "decide which side of the fence he's on".
"The American intervention has made that all the more urgent," he said.
In Dublin, Jose Manuel Barroso, the president of the EU executive, talked up the value of Britain being a member of the bloc, detailing policy areas where its influence had been positive.
"We believe it's very much in the interests of the European Union to have Britain at the centre of the European project," he said. "Many of our, let's say achievements, from the deepening of the single market to enlargement ... were possible also because of British commitment."
The prime minister's spokesman reiterated Cameron's determination to try to alter the nature of Britain's relationship with the EU.
"The prime minister's view is that he wants a change in Britain's relationship with the European Union and to seek fresh consent for that," he said.
The U.S. comments raised hackles elsewhere. Dominic Raab, a lawmaker from the Conservative party, told the BBC that Britain needed to do what was in its own interests and "not what is convenient for the Americans".
Nigel Farage, the leader of the anti-EU UK Independence Party, a party which has surged in the polls on the back of eurosceptic sentiment, was more blunt.
"The UK is a good and candid friend of the US, but having a historic special relationship should never mean being America's poodle," he said in a statement.
Daniel Hannan, a Conservative lawmaker in the European Parliament and a prominent eurosceptic, was equally scathing.
"Of all the bad arguments for remaining in the EU, the single worst is that we should do so in order to humor Barack Obama, the most anti-British president for nearly 200 years."
(Additional reporting by Luke Baker in Dublin; editing by Giles Elgood and Philippa Fletcher)