US secretary of state Antony Blinken’s visit to Ukraine this week reflects the Biden administration’s concern about the danger of Russian aggression against its western neighbour.

Though President Vladimir Putin has temporarily eased tensions by ordering Russian troops to pull back from the border, he remains determined to undermine the Ukrainian government’s control over its own territory. The US and its Nato allies should meet the threat with a co-ordinated response — which begins with providing Ukraine the weapons necessary to defend itself...