The US President and First Lady Jill Biden arrived at RAF Mildenhall in Suffolk on Thursday evening ahead of the G7 summit in Cornwall beginning on Friday.
Mr Biden and his wife disembarked Air Force One at about 7.45pm.
A large crowd of US Air Force personnel and their families were waiting for him inside a hangar at RAF Mildenhall.
Biden quipped that he forgets he is the US President as he addressed military personnel.
The US President – the Commander in Chief – told the servicemen and women to stand “at ease” as they stood to attention, adding: “I keep forgetting I’m president.”
The President is visiting RAF Mildenhall because the Suffolk base is home to the 100th Air Refuelling Wing, the only permanent US Air Force air refuelling wing in the European theatre.
The crowd rose to their feet shortly before 8pm in preparation for his arrival, with US flags decorating the walls along with a Union flag.
Speaking to the crowd, Mr Biden said his visit would show that “the United States is back” and democracies are standing together.
He will follow his trip to the G7 summit and Nato ministerial meeting with a visit to Switzerland for talks with Vladimir Putin.
Mr Biden told military personnel at RAF Mildenhall: “This is my first overseas trip as President of the United States.
“I’m heading to the G7, then to the Nato ministerial and then to meet with Mr Putin to let him know what I want him to know.
“At every point along the way we are going to make it clear that the United States is back and democracies of the world are standing together to tackle the toughest challenges and the issues that matter most to our future.”
Mr Biden has said “co-ordinated multilateral action” is needed to tackle climate change.
Speaking after his arrival at RAF Mildenhall in Suffolk on Wednesday evening, the US President said: “Over the next few days I’ll be participating in meetings with many of our closest partners, the G7 in Cornwall, then off to Brussels and the Nato summit and the EU summit.
“This diplomacy is essential because no single nation acting alone can meet all the challenges we face today because the world is changing.”
Mr Biden added: “To tackle this century’s most pressing challenges we have to do it together, we have to end Covid-19, not just at home but everywhere.
“There’s no wall high enough to keep us safe from this pandemic or the next biological threat we face, and there will be others.
“It requires co-ordinated multilateral action, we must all commit to an ambitious climate action if we’re going to prevent the worst impacts of climate change and global warming.”
US President Joe Biden said: “At the G7 we plan to launch an ambitious effort to support resilience and development around the world by investing in high-quality, high-standard physical, digital and health infrastructure.”
The move has been seen as a response to China’s efforts – through its “Belt and Road” initiative – to build international influence.
Mr Biden said the G7 must also establish new technologies and “norms of conduct in cyberspace”, including addressing the threat posed by ransomware attacks and he criticised the “autocrats who are letting it happen”.
“These are all critical national security issues in 2021 and we are going to be driving this agenda together with our G7 partners.”
Mr Biden also said the US commitment to the Nato principle of mutual protection – Article 5 – was “rock solid” and a “sacred obligation”.
The UK and US, as founding members of Nato, were part of “the strongest military and political alliance in the history of the world”, Joe Biden said.
The US President said: “Now we need to modernise our alliance, investing in our critical infrastructure, our cyber capabilities and to keep us secure against every threat we’ve faced over the last decade, and the new challenges we are about to face as well.”
During his trip, Mr Biden will warn Mr Johnson and the European Union not to “imperil” the Northern Ireland peace process, the US president’s national security adviser said, as they struggle to resolve a trade row.
The president will also use the visit to strengthen ties with allies at the G7 summit on Friday and join efforts to agree a strategy to vaccinate the world against coronavirus.
Mr Biden flew in to the UK on Air Force One, landing at the US airbase at RAF Mildenhall before heading on to Cornwall for Thursday’s talks with Mr Johnson and the G7 summit in Carbis Bay.
Ahead of the talks with Mr Johnson, Mr Biden’s national security adviser Jake Sullivan warned that the president harbours “very deep” concerns on the issue provoked by Brexit.
Mr Sullivan said the president believes the post-Brexit Northern Ireland Protocol is “critical” to ensuring that the Good Friday Agreement is protected, as Britain and the EU try to resolve the issue of checks in the Irish Sea.
The adviser told the BBC that both sides must continue with negotiations, adding: “But whatever way they find to proceed must, at its core, fundamentally protect the gains of the Good Friday Agreement and not imperil that.
“And that is the message that President Biden will send when he is in Cornwall.”
Mr Sullivan declined to say whether a failure to alleviate the Northern Ireland concerns could jeopardise a transatlantic trade deal, but added that “our concern runs very deep on the Northern Ireland issue”.
But the Prime Minister said he is “not worried” about the prospect of the summit being overshadowed by the row with the EU.
Asked about Mr Sullivan’s warning, Mr Johnson told broadcasters in Cornwall that he was “very, very optimistic” about the situation and said a solution is “easily doable”.
Mr Biden and his wife Jill will kick off the eight-day trip to Europe by meeting US personnel stationed at the Mildenhall airbase in Suffolk.
Having succeeded Donald Trump after his single fractious term in the White House, Mr Biden said the trip – which also takes in a Nato meeting and talks with Russia’s Vladimir Putin – was aimed at smoothing relations with allies which had been strained under his predecessor.