Donald Trump has said he and Boris Johnson have already started working on a free trade deal between the US and the UK.
The US president said the pair had spoken since Mr Johnson became prime minister and that they plan to spend time together to formulate an agreement.
Downing Street confirmed that talks between the two leaders had taken place on Friday evening and that they would meet at a G7 summit in Biarritz, France, next month.
Mr Trump told reporters: "We're working already on a trade agreement. And I think it'll be a very substantial trade agreement, you know we can do with the UK, we can do three to four times we were actually impeded by their relationship with the European Union. We were very much impeded on trade. And I think we can do three to four or five times what we're doing."
Number 10 said Mr Trump had expressed his commitment to an "ambitious free trade agreement", with formal talks to begin "as soon as possible after Britain leaves the EU".
Discussions over UK-US relations are likely to have begun in advance of Mr Johnson entering Number 10, as the PM had a phone call with Mr.Trump before his leadership victory was confirmed.
