It is not unprecedented for Western powers to impose sanctions on heads of government or heads of state. Past recipients of international punitive action include the likes of Robert Mugabe of Zimbabwe, Bashar al-Assad of Syria and Muammar Gaddafi of Libya.
But to sanction a despot is one thing, to sanction the leader of a major regional power is another. Targeting the head of a permanent member of the United Nations Security Council is rare, if not unprecedented, and to do so would plunge the UN into chaos.
Sanctioning Putin would make co-operation harder on other issues. The West needs his help to revive the Iran nuclear deal. That support might disappear if Putin were sanctioned.
It might also make it harder for Western leaders to meet Putin personally to discuss international crises. He might not be able to travel to Geneva or it might be illegal for the Western leader to meet him in Moscow.
Sanctioning Putin might also make him more popular at home – Mugabe certainly used his sanctions as an electoral asset. They also might not work in a technical sense. Russia experts say that much of Putin’s personal wealth is hidden away in the hands of third party proxies.
And then there is politics. Sanctions are often done – and are best done – with allies. It might be hard to get unanimous support say, within the European Union, for personal sanctions against the Russian leader.
Mr Biden also said on Tuesday that he would feel obliged to beef up Nato’s presence in eastern Europe if Russia invaded, but he repeated that there were no plans to send US troops to Ukraine itself.
The US has already put 8,500 combat-ready troops on alert to deploy at short notice. Russia has accused the US and NATO of “flooding” Ukraine with weapons and Western advisers.
Washington has also warned Russian ally Belarus that it would “face a swift and decisive response” if it assisted in an invasion.
Russia seized Ukrainian territory before, when it annexed Crimea in 2014. After Russian forces seized control, Crimea voted to join Russia in a referendum the West and Ukraine deemed illegal.
Russian-backed rebels also control areas of eastern Ukraine near Russia’s borders. That conflict has cost an estimated 14,000 lives, with a 2015 peace deal a long way from being fulfilled.
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