Joe Biden arrived in the UK on Air Force One ahead of the G7 summit in Cornwall.
His plane touched down at RAF Mildenhall in Suffolk on Wednesday evening, beginning his first overseas trip as US president.
A large crowd of Air Force members and their families waited for him inside a hangar, where he addressed them.
He said, “At every step of the way, we will make it clear that the United States is back and that the world’s democracies are coming together to tackle the toughest challenges and the issues that matter most to our future. “
The United Kingdom and the United States, as founding members of NATO, were part of “the strongest military and political alliance in the history of the world,” he said.
“We now need to modernize our alliance, invest in our critical infrastructure, our cyber capabilities and protect ourselves against all the threats we have faced over the past decade, as well as the new challenges we are also about to face. . “
After his stay at Mildenhall, Mr Biden flew to Newquay before heading to Tregenna Castle in Carbis Bay.
He will meet Prime Minister Boris Johnson on Thursday before the start of the G7 at Carbis Bay on Friday.
After the summit – which also includes leaders from Canada, Japan, France, Germany and Italy – Mr Biden and First Lady Jill Biden will meet with the Queen at Windsor Castle before the President meets with NATO leaders in Belgium, then Russian President Vladimir Putin in Switzerland.
Speaking of his meeting with Putin, Biden said the United States is not seeking conflict but will respond in “a strong and meaningful way” if Russia engages in harmful activities.
Mr Johnson has said he wants to discuss the COVID-19 pandemic and urge other leaders to do more to vaccinate the rest of the world, but it is likely that the growing trade line of Brexit and its effects on the process of peace in Northern Ireland will also arise.
Mr Biden’s national security adviser Jake Sullivan has warned the president has “very deep” concerns over the issue, adding that the post-Brexit protocol in Northern Ireland is “critical” to ensuring the protection of the Good Friday agreement.
During Mr. Biden’s flight across the Atlantic, his press secretary Jen Psaki and Mr. Sullivan told reporters what else was on Mr. Biden’s agenda:
• Increase in vaccine supply – the United States announced Wednesday evening that it donate 500 million COVID-19 vaccines to the poorest countries
• Following discussions on possible exceptions to intellectual property laws allowing the production of more vaccines in the world, Mr Sullivan said he did not anticipate contention but “convergence” on the issue
• Mr Sullivan said moves to vaccinate poorer countries faster is “the right thing to do” and the smart thing to do in terms of stopping new variants of the virus. Mr Biden also wants to show that democracies can lead the fight
• Mr. Biden will meet Russian President Vladimir Putin in Switzerland where he will discuss the increase in ransomware attacks attributed to Russian hackers
• The conflict in Syria will be discussed, as will concerns about Russia’s new nuclear systems.
• Mr Biden and Mr Johnson should update the Atlantic Charter. The charter was first announced in 1941 by the United States and the United Kingdom, setting out a vision for the post-war world.