Dmitry Medvedev, a former Russian president and close ally of Russian President Vladimir Putin, has warned that if the United States fuels the Ukraine conflict, it will face a World War III.

Medvedev, who serves as deputy chairman of Russia's security council, told Russian RT broadcaster on Saturday that if the next U.S. leader continues to fuel the Russia-Ukraine conflict, it will be a very bad choice as it will lead to a path to hell.

Medvedev reportedly said that it will open up the path to a third world war, urging U.S. presidential candidates Donald Trump and Kamala Harris to realize it.

Russia has been signaling signs to the West that Moscow will respond with its nuclear weapons if the United States and its allies help Ukraine fire longer-range weapons deep into Russia.

Medvedev reportedly warned the United States that it was wrong to believe that Russia will never "cross a certain line" when it comes to the deployment of nuclear arms.