President Biden arrived in Europefor his first foreign trip bearing what could be a game-changing pledge: 500 million doses of Pfizer-BioNTech vaccines to be shared with low- and middle-income countries over the next year.

The state of play: The remaining G7 members — Canada, the EU, France, Germany, Italy, Japan and this year’s hosts, the U.K. — are set to pledge at least another 500 million to bring the total to 1 billion by mid-2021, per a draft communique seen by Bloomberg.

• After months of vaccine hoarding by the world’s wealthiest countries, that's a whiplash-inducing shift — particularly from the U.S., which wasn’t even allowing vaccine exports until recently.
• But a year is a long time in the life of the pandemic, so urgency is a key element here.
• The U.S. already has sufficient supply to cover all domestic demand, while the other G7 countries will reach that point by June (Canada), July (France, Italy, Germany, U.K.) or August (Japan), per an analysis from the One Campaign.

What to watch: The G7 is also set to call for a new investigation into the origin of the pandemic, per the draft communique.

• The key unresolved question is what the countries will announce on climate change — in particular how much money they'll make available to help poorer countries decarbonize their economies.
• The summit's host, U.K. Prime Minister Boris Johnson, is reportedly pushing for a climate “Marshall Plan.”

Biden’s next stop will be Brussels for his first NATO summit (June 14–15).

• The alliance went through something of an identity crisis over the last four years, with Donald Trump calling it obsolete and French President Emmanuel Macron declaring it brain dead.
• Biden will have to reassure allies that America is indeed back while also encouraging them to invest in their own defense, says Stacie Pettyjohn of the Center for a New American Security.
• Questions will remain about whether America is back to stay, she adds: “There’s a fear that President Trump could return, or that another nationalist leader could be elected.”
• It’s also not clear to what extent Biden’s top geopolitical priority —countering China — will be on the agenda.

What to watch: Biden will meet with Turkish President Recep Tayyip Erdoğan while in Brussels.

• The two have some uncomfortable history, and the June 14 meeting comes with deep wounds in the relationship over Russia, Syria and Erdoğan's autocratic tilt.
• The meeting is so politically sensitive in Turkey that senior officials are skipping public events so as to avoid questions about it, Menekse Tokyay reports for Axios from Ankara.

Biden’s last stop is Geneva for his much-anticipated summit with Vladimir Putin.

• Biden says his goal is to lay the groundwork for a "stable and predictable" relationship with Russia.
• On the Russian side, there's a split between the Foreign Ministry and the security establishment, says Tatiana Stanovaya of Carnegie Moscow.
• The former sees the summit as a “last chance” to put long-standing strategic issues on the table, while the latter wants a more “pragmatic and realistic agenda” that concludes with channels of communication in place to handle day-to-day challenges going forward.

Flashback: Putin arrived at his 2018 summit with Trump in Helsinki with high hopes and a series of proposals for the future of the relationship, Stanovaya says.

• Now, "there are fears [in Moscow] that the U.S. side will use this summit to make a point, and after this, the dialogue will fizzle out."

Go deeper:

• Biden's European optimism collides with reality
• Team Biden tiptoes around vaccine-for-migration cooperation
• Deep dive on Biden's big trip