Ukraine's new tanks an upgrade - but may arrive too late

The M1 Abrams tanks the US will send to Ukraine are a significant upgrade in the arming of Kyiv, but will not make any difference to the next phase of the war.

The decision to send them is an abrupt reversal after longstanding Pentagon arguments that they are a poor fit for the Ukrainian battlefield.

But the announcement itself does make a difference.

"It unlocks the German decision to send Leopard 2 tanks and for others who have Leopard tanks to send them as well," Kurt Volker, the former US Special Representative to Ukraine, told the BBC.

Western allies want to build up Ukraine's armoured vehicle capacity in the next six to eight weeks to help prepare it for an expected Russian spring offensive.

It will take much longer than that to get the Abrams to the battlefield and to train Ukrainians to look after them. German-made Leopards, on the other hand, can be deployed relatively quickly and are easier to operate.