Ukraine fear the aid envoy sent to them from Russia is an "invasion dressed up as humanitarian aid."
The 280 trucks, which have travelled 300 miles from Moscow, are said to contain food, water and electrical generators, but the Ukraine has so far refused to let them in.
Russia claims any suspicion about the aid supplies to the region are "absurd."
But acting Ukraine Ambassador to the UK Andrii Kuzmenko said it "could be a pretext for war."
ITV News Correspondent Lewis Vaughan Jones has this report: