The US State Department's top official in Europe said America wants Britain to remain part of the European Union.
Philip Gordon said the saying the EU has "increasing weight in the world" and any referendum in the UK would risk turning the country "inward."
The comments are timely, as Political Editor Tom Bradby reports:
More top news
Facebook says it will start test flights later this year of a solar-powered drone that aims to provide remote areas with the internet.
Children's charity Kids Company is being investigated by the Metropolitan Police over criminal allegations.
A senior employee at a 4-star London hotel has been jailed for six years for raping a man who he lured to a fake job interview.