New reports say that US President Joe Biden has allowed Ukraine to use American weapons to conduct strikes inside Russian territory. So far, all western weapons supplied to Ukraine came with a limitation: Ukraine could not use them to attack Russian soil. But the latest Russian offensive on Ukraine's second-largest city, Kharkiv, has forced Kyiv's western allies to rethink their stance. In early May, the UK gave Ukraine permission to use its weapons to strike Russia. Britain was followed by France and Germany who made similar announcements. Now, it seems the US has also untied Ukraine's hands. But how will Russia react to this latest escalation?