Russia's nuclear rules say it can use atomic weapons if the country — or one of its allies — is attacked, especially if the attacker is a non-nuclear nation backed by a nuclear power. That clause could be seen as applying to Ukraine,

President Donald Trump has finally found a way to like arming Ukraine: ask European allies to donate their weapons, and sell them American replacements.

The change in Trump’s approach may also mean that the $US8 billion (£6 billion) of frozen Russian assets in the US (and US$223 billion in Europe) could be released to aid Ukraine, which would provide a ready means to pay for the US arms transfers.