But for his parting thought he decided to ad-lib. "For God's sake, this man cannot remain in power," he said, speaking of the architect of Ukraine's misery - Russian president Vladimir Putin. His message was met with applause from the Poles and Ukrainians in the audience, but back at home in Washington mouths dropped.
Within minutes, the White House put out a corrective - no, the US wasn't seeking regime change in Moscow. Biden had somehow been mistaken.
This Biden gaffe won't be so easy to shake
Perhaps his administration was so quick off the mark because it has had practice.
It was not the first time their boss had gone off-script, it was not even the first time this week.
During his four-day trip to Europe, the White House has had to walk back several of the 79-year-old commander-in-chief's remarks.
The administration clarified the US "would not" use chemical weapons after the president said the country would respond "in kind" to any Russian chemical attack. They also cautioned that US troops would not be going to Ukraine after Biden told the 82nd Airborne Division stationed in Poland of the horrors they were "about to see" in the neighbouring war.
Back in January, the president had to clarify his stance on a potential war in Ukraine, walking back remarks from the prior day's news conference during which he suggested a "minor incursion" would elicit a lesser response than a full-scale invasion of the country.
Dmytro Kuleba, Ukraine's Foreign Minister, hit out at the comment later, saying that a country "can't be half invaded".
Many of Biden's gaffes can be written off. But this one won't be so easy to shake.
Putin believes the West is coming for him
The off-hand comment will have confirmed what Putin has believed all along - that the US's real, unspoken, policy is regime change, thereby ensuring the war he has waged becomes a fight not just for Ukraine but also for Putin's survival.
It is said Putin was obsessed with the videos of Moammer Gaddafi's final moments, when the dethroned Libyan leader was discovered hiding in a sewer by rebels (with the help of Nato intelligence) before being shot and bayoneted to death.
The image of a strongman brought down by the powerful alliance became an instructive one.
Putin has believed the West was coming for him since, so the US president openly calling for his ouster will play into his worst fears.
"Hawks in the administration and outside will love it," tweeted Aaron David Miller, former State Department adviser now at Carnegie Endowment.
The Kremlin responded by saying this was a matter "not to be decided by Biden, but by the people of the Russian Federation".
Russian state TV, meanwhile, had already begun playing clips of the final lines of the speech on repeat.
Biden's visit to Warsaw this weekend came 25 years after another historic speech he made in the Polish capital as a US senator after the fall of the Soviet Union, when he urged European partners not to be complacent.
The top Democrat on the Senate Foreign Relations Committee at that time, Biden was among the loudest - and most articulate - voices in championing Nato's expansion in Eastern Europe in the late 1990s.
But the once-skilled orator, it seems, can no longer be trusted to deliver the message.
