The United States will respond if Russian President Vladimir decides to use chemical weapons in Ukraine, US President Joe Biden said.

"We would respond, we would respond if he [Putin] uses it. The nature of the response would depend on the nature of the use," Biden said at a news conference in Brussels on Thursday.

The president said he would not share intelligence data on whether there is a real risk of Russia using chemical weapons in Ukraine.

At the same time, on the question of whether the use of chemical weapons by Russia will lead to a military response from NATO, Biden said that NATO "will make this decision at the time."