9 January 2013 Last updated at 13:00 ET

Article written by Nick Robinson Political editor

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US official's comments illustrate Cameron's EU dilemma

Mr Gordon suggests Europe is more influential with a strong British voice

Even before the prime minister has uttered a word of his long-awaited speech on Europe - a speech in which he is expected to call for a re-negotiation of the UK's relationship with the EU followed by a referendum - David Cameron is being warned about the consequences.

Philip Gordon may not be a household name in Washington DC let alone in the UK but as assistant secretary for European affairs he is the most senior official in the US State Department who deals with Europe.

On a visit to London, Mr Gordon told reporters that it was in America's interests to have a growing relationship with the EU and for Britain to have a strong voice in Brussels.

He also echoed the concerns of some business leaders that "referendums have often turned countries inward" warning that "it is best for everyone, we think, when leaders have the time to be able to focus on common challenges rather than spending their time on internal workings".

This is yet further explanation of why a speech the prime minister is expected to deliver in the Netherlands within the next two weeks has proved so hard to write and may prove so controversial.