Britain’s membership of the European Union has magnified its role on the global stage, U.S. Secretary of State John Kerry said on Tuesday.

Kerry was talking to reporters in London just a few weeks after President Barack Obama visited the capital to urge Britons to stay in the EU, warning that the country would be at “the back of the queue” for a U.S. trade deal if it left.

Last week Secretary Kerry told university students in Boston to prepare for a “borderless world”.

Speaking at Northeastern University, he said: “Many of you were in elementary school when you learned the toughest lesson of all on 9/11… There are no walls big enough to stop people from anywhere, tens of thousands of miles away, who are determined to take their own lives while they target others.”

“So I think that everything that we’ve lived and learn tells us that we will never come out on top if we accept advice from sound-bite salesmen and carnival barkers who pretend the most powerful country on Earth can remain great by looking inward,” Kerry added. “And hiding behind walls at a time that technology has made that impossible to do and unwise to even attempt.”

“The future demands from us something more than a nostalgia for some rose-tinted version of the past that did not really exist in any case,” he said. “You’re about to graduate into a complex and borderless world.”

His comments on Britain and the EU however are hardly novel. In February he said in a speech: “Europe is going to emerge stronger than ever, provided it stays united and builds common responses to these challenges… Now obviously, the United States has a profound interest in your success, as we do in a very strong United Kingdom staying in a strong EU.”

Britons vote in a referendum on June 23 on whether the country should remain in the bloc.

Reuters contributed to this report