Ukraine is at a decisive moment on the battlefield, U.S. Defense Secretary Lloyd Austin said.

"The stakes are too high. Ukraine is experiencing a decisive moment on the battlefield. And we are seeing what President Zelensky warned us about. After failing to seize Kiev and re-evaluating its combat objectives, Russia has shifted its focus to the Donbass. And we cannot underestimate the challenge Ukraine faces," Austin said at the opening of the Ukraine defense contact group meeting in Brussels on Wednesday.

He stressed that he was personally grateful for the significant security assistance the contact group has provided to Ukraine.

"But we cannot afford to give up and slow down," Austin added.