The threat is said to have been made in a phone call between the two leaders shortly before Vladimir Putin ordered the Russian invasion of Ukraine.
Boris Johnson and other Western leaders had then visited Kyiv to show their support for Ukraine in an attempt to ward off a Russian attack.
- He kind of threatened me at one point and said "Boris, I don't want to hurt you, but with a robot it would only take a few minutes" or something like that, says Boris Johnson in the BBC documentary, which will be broadcast on Monday and which depicts the growing rift between the Russian leader and the West in the years before the invasion of Ukraine.
Rejected by Russia
The Kremlin refutes the information through its spokesman Dmitry Peskov, who describes the whole thing as "a lie", reports Reuters.
The documentary also shows Ukrainian President Volodymyr Zelensky reflecting on his thwarted ambition to join the NATO defense alliance before the Russian offensive began.