Secretary of State Mike Pompeo predicted Thursday that Brexit would bring "enormous benefits" to the United States and the UK, during a visit to Britain on the eve of its historic departure from the European Union.

Ahead of talks with Prime Minister Boris Johnson about a post-Brexit trade deal and other key issues, Pompeo said he was optimistic about Britain's nearly half a century of EU membership ending late Friday.

"There were things that the United Kingdom was required to do as part of being a member of the EU, and they'll be able to do them differently now," Washington's top diplomat told a think-tank audience in London.

"Some of this will be worked out through the free trade agreement, some of it will be worked out by entrepreneurs just kicking it," he said, alongside British Foreign Secretary Dominic Raab.