Biden authorises Ukraine to use ATACMS inside Russia, angering Moscow, which accuses Washington of escalating conflict.

The United States has given Ukraine permission to use US-made ATACMS missiles to hit targets inside Russia.

Warning comes as Putin lowers threshold for using Russia nuclear arsenal in move decried as 'irresponsible' by the West.

US arms export growth was driven by countries seeking to replenish weapons stocks that were donated to Ukraine.