The commander of Ukraine’s ground forces General Oleksandr Syrskiy, in an exclusive interview with ABC News' Chief Foreign Correspondent Ian Pannell, said the world should be worried about Russian President Vladimir Putin's threat to use nuclear weapons.

This follows Putin's threat that Russia would resort to using nuclear weapons in its war against Ukraine following a series of setbacks for Moscow on the battlefield.

"We are and should be worried," Syrskiy told ABC News.