US President Joe Biden  (Photo: Mindaugas Kulbis/AP)

The UK is Biden’s first stop. The visit, which comes just a month after British Prime Minister Rishi Sunak visited the White House, reflects the strong relationship between the UK and the US.

On Monday, Biden met Sunak to discuss the conflict in Ukraine and the NATO summit in Lithuania on Tuesday and Wednesday that both of them will attend.

Biden also met King Charles III at Windsor Castle in west London, where the late Queen Elizabeth II hosted Presidents Barack Obama and Donald Trump. The two leaders discussed climate change and the environment, which Charles has strongly supported for the past five decades.

The centerpiece of Biden's European trip is attending the NATO Summit in Vilnius for two days. NATO, the US-led military alliance, has become more united since the outbreak of the Russia-Ukraine conflict, but it is experiencing internal disagreements over the admission of new members and support for Kyiv.

The Summit will test Biden's ability to unite NATO members, with Sweden's attempt to join the alliance blocked by objections from Turkey and Hungary and NATO members squabbling over admitting Ukraine.

While Lithuania and NATO countries in Eastern Europe want to accelerate the admission of Ukraine, the US, Germany and some others favor a more cautious approach, fearing the prospect of NATO getting drawn into a direct conflict with Russia. Biden will deliver a speech in which he will share his vision of a strong, confident America flanked by strong, confident allies and partners taking on the significant challenges of our time, from Russia’s special military operation in Ukraine to the climate crisis.

Biden’s final stop in Europe will be Helsinki to attend the US-Nordic Leaders’ Summit. This will be the first meeting between the US and the Nordic countries during the Biden administration.

In Helsinki on Thursday Biden and the leaders of the Nordic countries will discuss security cooperation in the Arctic. Both China and Russia will attend. The participants will also discuss technology cooperation, including 5G, artificial intelligence, and a climate and clean energy deal.

Beyond foreign affairs, Biden's intends this trip to show the American voters the importance of continuing his strategy of supporting Ukraine, which his Republican election rivals have expressed skepticism about.