Vladimir Putin
And the West needs "to get to Trump quickly," according to a former national security adviser.
PM Keir Starmer has previously refused to divulge any "operational details" around the weapons' usage.
Not exactly the news any potential negotiators wanted to hear.
The US has closed its embassy in Kyiv after warnings of a potential significant air attack.
Downing Street said "it’s the latest example of irresponsibility that we have seen from the depraved Russian government".
Russia has actually had a "really terrible performance."
The Russian president is attacking energy infrastructure and killing civilians, No.10 says.
But Putin himself stayed silent on Sunday night.
Kyiv finally has permission to use US-supplied weapons for targets beyond Russia's borders.
Ukraine's president Volodymyr Zelenskyy has slammed their phone conversation, saying it had opened "Pandora's Box".