Kerry heads to London after Brexit

US Secretary of State John Kerry yesterday expressed regret that Britain has chosen to leave the European Union and vowed Washington will maintain close ties with the bloc.

Kerry, who flies to Brussels and London today for crisis talks with EU and British leaders, said the ideal of unity must remain paramount as Britain negotiates "Brexit".

"An EU united and strong is our preference for a partner to be able to work on the important issues that face us today," Kerry told reporters during a visit to Rome.

"One country has made a decision, obviously it's a decision that the United States had hoped would go the other way," he said.

Washington was dismayed last week when British voters chose to leave Europe, a decision that triggered global economic uncertainty and fears other EU members will follow suit.

But Kerry said he had no doubt that Europe would pull together and reassure the markets, noting that even without Britain the EU single market counts 455 million consumers.

Kerry arrived in Rome yesterday on a planned visit to have lunch with Gentiloni and a working dinner with Israeli Prime Minister Benjamin Netanyahu.

But officials on his flight said that today  he would fly on to EU headquarters in Brussels to meet EU foreign policy chief Federica Mogherini. From Brussels, Kerry will continue to London to see Foreign Secretary Philip Hammond.

Hammond and Kerry are expected to hold a joint news conference before Kerry leaves to return to Washington.