The United States will send another  $1.1bn Patriot missile air defence system to Ukraine in the coming days as the war-ravaged nation struggles to fend off Russian attacks on its cities and energy grid.

The new Patriot system would be at least the second that the US has sent to Ukraine.

The Patriot, considered the United States’ best air-defence weapons, can shoot down incoming missiles before they hit their intended targets and is already used by Israel and Saudi and Emirati forces in Yemen.

The critical systems are considered incredibly rare, even for the United States. Pentagon officials refuse to disclose how many are in its arsenal, but one senior military official said that the Army has deployed only 14 of them, in the US and around the world.  

Patriot batteries can project defences out some 600 miles and are often used to target and shoot down long-range ballistic missiles and aircraft from hundreds of miles away.

The Patriot is by far the most expensive single weapon supplied by the US to Ukraine, with the total cost around $1.1 billion (£784m): $400 million (£303m) for the system and $690 million (£541m) for the missiles.

Follow the latest updates below