The US will increase its military presence across Europe as Nato agreed a "fundamental shift" in its response to Russia's invasion of Ukraine.
A permanent army headquarters will be created in Poland, while new US warships will go to Spain, fighter jets to the UK and ground troops to Romania.
Mr Biden said Nato was "needed now more than it has ever been".
The alliance is having its biggest overhaul since the Cold War, Nato head Jens Stoltenberg said.
The new plan in response to Russia's invasion will mean more than 300,000 troops at high readiness next year, up from the current level of 40,000.
Mr Biden told a summit in Madrid that Nato would be "strengthened in all directions across every domain - land, air and sea".
The UK's Ministry of Defence (MoD) has also said it is significantly increasing the availability of forces to Nato's collective defence, with more warships, fighter jets and land forces on standby - although the MoD said it would not give details on numbers as they are "militarily sensitive".
https://www.bbc.co.uk/news/world-europe-61983555