Biden, 81, who has for 13 days faced questions about his fitness for office after fumbling a June 27 debate, hopes the international event will help him stage a comeback of sorts, surrounded by allied leaders he has spent his three years in office cultivating.
After calling the 32-member collective security alliance "stronger than it's ever been" in a forceful speech on Tuesday, Biden and the other NATO leaders now turn to their difficult work.
Leading their agenda is the two-plus year stand-off between the West and Russia over Ukraine.
But the summit also gives leaders a chance to address other vexing security issues, including the Israel-Gaza war and deepening bonds between Russia, Iran, China and North Korea.
President Joe Biden will also host a dinner for NATO heads of state and government. (AP PHOTO)
November's US elections could presage a sharp change in Washington's support for Ukraine and NATO.
Republican candidate Donald Trump, 78, has questioned the amount of aid given to Ukraine in its battle against Russia's invasion, as well as US support for allies generally.
On the sidelines of the summit on Wednesday, Biden is expected to meet British Prime Minister Keir Starmer for their first face-to-face talks since his Labour Party won a landslide election victory that ended 14 years of Conservative rule.
The countries are key trans-Atlantic allies.
Biden will also host a dinner for NATO heads of state and government, an event that would not usually draw attention but has come into focus given concerns over whether Biden can handle the demands of the presidency for another four years.
A senior NATO official said this week that Russia lacks the munitions and troops to start a major offensive in Ukraine, but that it could sustain its war economy for three to four more years.
Ukraine also has not yet amassed the munitions and personnel it needs to mount its own large-scale offensive operations, the official said.
Ukrainian President Volodymyr Zelenskiy wants more assistance from NATO. (AP PHOTO)
Hoping to change the course of the grinding conflict, Ukrainian President Volodymyr Zelenskiy wants the alliance to send more weapons and money and offer security guarantees.
He will meet Republican House of Representatives Speaker Mike Johnson, a Trump ally, at the Capitol on Wednesday.
Zelenskiy is attending parts of the NATO summit as a guest but Ukraine ultimately wants to join the group to ward off further future attacks by Russia.
That will not happen soon. Candidates have to be approved by all alliance members, some of which are wary of provoking a direct conflict with Russia.
Still, some members want the alliance to make clear that Ukraine is moving towards NATO "irreversibly" and are keen for language in a summit statement beyond the alliance's pledge in 2023 that "Ukraine's future is in NATO".
Already, NATO members have announced the delivery of five additional Patriot and other strategic air defence systems to help Ukraine.
Still more aid announcements were expected at the summit, which marks the alliance's 75th anniversary.
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