A Ukrainian military spokesman says a humanitarian convoy being dispatched to eastern Ukraine by Russia will not be admitted into the country.
Andriy Lysenko, a spokesman for Ukraine's National Security and Defense Council, said the convoy will not be let in until it has been certified by the International Committee of the Red Cross (ICRC).
Presidential aide Valeriy Chaly said Ukraine would not allow any Russian aid into the country if it was accompanied by the Russian military or members of Russia's Emergencies Ministry.
A convoy of nearly 300 Russian trucks headed for Ukraine early on August 12, one day after agreement was reached on an international humanitarian relief mission.
Russian officials said the trucks were carrying 2,000 tons of aid, from baby food to sleeping bags.
The ICRC said it had no information on what the trucks were carrying or where they were going.
Ukrainian and Western officials have voiced concern that Russia could use the pretext of humanitarian aid to send troops into eastern Ukraine where government forces are fighting pro-Russian separatists.
Chaly said the Russian trucks will have to be unloaded at the border and the goods must be transported by ICRC vehicles.
The Ukrainian government also says aid must cross at a government-held border crossing. At least 100 kilometers of the border is currently in separatist hands.
The Russian Emergencies Ministry, which manages the initiative, has not said where the convoy plans to cross the border.
Former Ukrainian President Leonid Kuchma, who, along with the Russian ambassador, has taken part in three-way negotiations to end the fighting, said the convoy would be crossing from Russia into the Kharkiv region, away from areas affected from the fighting.
Ukraine and the West accuse Russia of aiding the separatists with weapons and expertise. On August 11, NATO Secretary-General Anders Fogh Rasmussen said that he saw a "high probability" of Russia attempting to intervene militarily in Ukraine "under the guise of a humanitarian operation."
Western officials have warned against any unilateral military action in Ukraine under any pretext.