Johnson had a "great visit to the US" and "held valuable discussions" with senior members of Trump's team, he wrote on Twitter. "We are the number two contributor to defence in NATO. We are America's principal partner in working for global security and, of course, we are great campaigners for free trade," he said in a video message posted online by British media.

"We hear that we are first in line to do a great free trade deal with the United States," Johnson said. "So, it's going to be a very exciting year for both our countries." Johnson met Trump's son-in-law, Jared Kushner, and chief strategist, Steve Bannon.

The positive signals from them are likely to boost Prime Minister Theresa May's efforts to refocus Britain's trade relations as she negotiates the country's exit from the European Union.

Trump tweeted on Saturday he was looking forward to meeting May in Washington this spring. "Britain, a longtime US ally, is very special!" he wrote.