US secretary of state John Kerry has said that Britain’s vote to leave the European Union might never be implemented and that London is in no hurry to go.

Speaking one day after talks with Prime Minister David Cameron, Mr Kerry said the outgoing British leader feels “powerless” to negotiate a departure he does not want.

“This is a very complicated divorce,” Mr Kerry told the Aspen Ideas Festival, referring to Britain’s negotiated exit from the EU after last week’s Brexit referendum.

Mr Kerry, who visited Downing Street on Monday, said Mr Cameron was loath to invoke Article 50 of the Lisbon treaty, which would trigger a two-year timetable for departure.

London, Mr Kerry explained, does not want to find itself boxed in after two years without a new association agreement and to be forced out of the EU without one.

Mr Cameron “feels powerless — and I think this is a fair conclusion — to go out and start negotiating a thing that he doesn’t believe in and he has no idea how he would do it,” he said. “And by the way, nor do most of the people who voted to do it,” Mr Kerry said, apparently referring to “Leave” campaigners such as Boris Johnson.