Barack Obama has warned that Britain will lose influence if it leaves the European Union. In an interview with the BBC broadcast on Thursday night, the US president said the EU “made the world safer and more prosperous” and confirmed Washington’s longstanding view that Britain should remain a member. Rather than avoiding taking a stance on the issue, which will be the subject of a referendum in Britain – probably next year, he said: “Having the UK in the EU gives us much greater confidence about the strength of the transatlantic union, and is part of the cornerstone of the institutions built after [the second world war] that has made the world safer and more prosperous. We want to make sure that the United Kingdom continues to have that influence.”

Obama’s comments will be welcome in Downing Street, where David Cameron intends to lead the referendum campaign for Britain to remain in the EU following his renegotiation of the terms of membership. Barack Obama is not one of them

Although Cameron has not ruled out recommending withdrawal in the event of his renegotiation failing, the prospect of his not eventually committing himself to continued EU membership seems extremely remote.

Pro-Europeans argue that leaving the EU would diminish Britain’s international influence, and Obama’s comments will help them to make that case.

In his interview, Obama said that Britain was the US’s “best partner” because of its willingness to project power beyond its “immediate self-interests to make this a more orderly, safer world”.