Putin draws a nuclear red line for the West

President Vladimir Putin has drawn a "red line" for the United States and its allies by signalling that Moscow will consider responding with nuclear weapons if they allow Ukraine to strike deep inside Russia with long-range Western missiles.

But some in the West are asking: does he actually mean it?

The question is critical to the course of the war. If Putin is bluffing, as Ukraine and some of its supporters believe, then the West may feel ready to deepen its military support for Kyiv regardless of Moscow's threats.

If he is serious, there is a risk - repeatedly stated by Moscow and acknowledged by Washington - that the conflict could turn into World War Three.

In the latest in a long series of warning signals, Putin on Wednesday extended the list of scenarios that could lead to Russia using nuclear weapons.