'We are and should be worried' of Putin's nuclear threat, Ukrainian general says: Exclusive

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.

Late last month, Putin issued a thinly veiled 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.

You can watch more of Ian Pannell's full interview with General Oleksandr Syrskiy on ABC's "Good Morning America" on Monday.

The Ukrainian general is confident that his country is winning the fight against Russia, despite the challenges of war.

"Of course, I think we are winning. Because first and foremost, we are winning the psychological battle," Syrskiy said. "We have success on the battleground, but the war is difficult."

Syrskiy, the commander of the Army of the Armed Forced of Ukraine, won the battle of Kyiv in the spring and the battle of Kharkiv in September. The successful surprise counteroffensive rapidly liberated thousands of square miles of occupied territory, forcing the Russians back towards their border.

Last month, Putin accused Ukraine of terrorism after an explosion destroyed parts of a bridge connecting occupied Crimea to Russia, a vital supply route for Russian forces.

"There hasn't been any wars at that scale in Europe, or elsewhere in the world, since the Second World War. And we understand that this war is about the survival of our people and our state and this is why we have no other option but to win," Syrskiy said.