LONDON (AFP/REUTERS) - President Donald Trump said on Friday (July 26) he had spoken by phone with new British Prime Minister Boris Johnson and that discussions on a major trade deal were already under way.

"I predict he'll be a great prime minister," Trump said, calling Johnson a "good guy" minutes after ending the conversation.

A "very substantial" trade deal with post-Brexit Britain is possible, Trump told reporters.

A statement from Downing Street in London said the two leaders had agreed to start talks as soon as possible after Britain leaves the European Union.

The statement said Johnson and Trump expressed commitment to delivering an "ambitious free trade agreement".

It added that they will meet at the Group of Seven (G-7) Summit in Biarritz, France, in August.

The leaders also discussed recent tensions with Iran and the need for the two countries to work together on the issue, the statement added.