United States President Joe Biden on Friday said that a direct clash between members of the North Atlantic Treaty Organization, or NATO, and Russia would lead to the third world war.

He reiterated that American forces will not fight the war in Ukraine against Moscow.

“We will not fight a war against Russia in Ukraine,” Biden said while addressing reporters, according to the White House. “Direct confrontation between NATO and Russia is World War III – something we must strive to prevent.”

Russia on February 24 had invaded Ukraine. Russian President Vladimir Putin has described the invasion as a “special military operation” aimed at dislodging the “neo-Nazis” ruling Ukraine.

According to the United Nations human rights office, 474 civilians have been killed and 861 injured in Ukraine. On the Russian side, over 498 of its troops have died, according to the country’s military.

During Friday’s address, Biden said that the United States will continue to provide support to Ukraine in the war.

“We are going to continue to stand together with our Allies in Europe and send an unmistakable message,” he said. “We will defend every single inch of NATO territory with the full might of a united and galvanised NATO.”

Biden further said that Putin’s war against Ukraine will never result in a victory. “He [Putin] hoped to dominate Ukraine without a fight. He failed.”

The American president also responded to the White House’s claims that Russia may use chemical weapons in Ukraine.

“I’m not going to speak about the intelligence. But Russia would pay a severe price if they used chemical weapons,” Biden told reporters when questioned about having evidence regarding the claim.

On March 9, the White House Press Secretary Jen Psaki had warned that such weapons could be used in the Ukraine conflict. “We should all be on the lookout for Russia to possibly use chemical or biological weapons in Ukraine, or to create a false flag operation using them,” she had said.