The sprawling Russian convoy, allegedly carrying humanitarian aid to people trapped by conflict in the rebel held town of Luhansk, is some 40km from the border with Ukraine.
The vehicles are close to the Izvarine border crossing, which is controlled by pro-Russian separatists.
The white trucks have been joined along the way by a number of Russian military vehicles and aircraft.
“We will go where we are told to go. It’s a hot day today, but everything is OK, the truck is driving well,” said one of the convoy’s 280 drivers.
Ukraine says it will not allow the trucks to enter the country unless the contents are first checked by Ukranian customs and then handed over to the Red Cross for distribution.
Andriy Lysenko is from Ukraine’s National Security and Defence Council: “Even in the event that a decision will be made to transport aid through the border controlled by the ‘terrorists,’ the cargo will be examined by Ukrainian border guards and passed on to the Red Cross. However, the entire responsibility for the safety of the contents will be Russia’s. Russia controls the arms and the mercenaries.”
Kyiv has dispatched its own convoy to the region, some 75 trucks carrying 800 tons of sugar, grain, and tinned goods.
The supplies will handed to the Red Cross for eventual distribution in Luhansk.