The US president thinks it's unlikely a missile which killed two people in Poland was fired by Russia.
Investigations are underway following the explosion in a village near the Ukrainian border yesterday.
Moscow has denied being responsible.
Sky's Cordelia Lynch is at the G20 summit of world leaders – and says The Associated Press news agency has been speaking to those close to an initial American investigation.
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'These officials say the Ukranians have been trying to defend themselves against the Russians aiming at their electrical infrastructure- that further builds on the suspicions of Joe Biden'
