Washington: US President Joe Biden once again warned Russia that NATO intervention is inevitable if Russia used chemical weapons on Ukraine.

He also warned Moscow to avoid provoking World War-3. US President's reaction came after Russia and Ukraine decided to use chemical weapons in the war. Western Nations urges Moscow to end the war.

Biden reacted after Russia accused Ukraine and the United States of developing biological and chemical weapons -- in what Western nations says is a ruse to lay the ground for Moscow's own possible use of them in the conflict.

"I'm not going to speak about the intelligence, but Russia would pay a severe price if they used chemicals," Biden said as he announced a raft of new sanctions against Moscow.

At the request of Russia, the UN Security Council is holding an emergency meeting Friday on the alleged manufacture of biological weapons in Ukraine.

Biden also moved Friday to end normal trade relations with Russia, further racheting up pressure on President Vladimir Putin after the bloody invasion of Ukraine.

The United States, like other Western nations, is sending millions of dollars of weapons such anti-aircraft and anti-tank missiles to Ukraine, as well as sharing intelligence.

But Biden again underlined that US forces would not fight in Ukraine, despite the desperate pleas of many Ukrainians.

In 2018, Moscow accused the United States of secretly conducting biological weapons experiments in a laboratory in Georgia, another former Soviet republic that, like Ukraine, has ambitions to join NATO and the European Union.

The Friday meeting was announced by Russia's Deputy U.N. Ambassador Dmitry Polyansky in a tweet linking to the Russian Ministry of Defense, claiming analysis of documents about U.S. "military biological activities" in Ukraine, with a half-dozen documents attached with graphs and charts., CBS news reported.  

U.S. Ambassador to the U.N. Linda Thomas-Greenfield told Security Council members on Friday that Russia asked for the council meeting "for the sole purpose of lying and spreading disinformation."

"I will say this once: Ukraine does not have a biological weapons program, and there are no Ukrainian biological weapons laboratories supported by the United States. Not near Russia's borders, not anywhere," Thomas-Greenfield said.

Her comments came as Russia's Foreign Affairs Ministry claimed that Ukrainian groups under control of "representatives of American special services have prepared several potential scenarios of the use of toxic chemicals in order to carry out various types of provocations," with the objective of accusing Russia of using chemical weapons against civilians, CBS news reported.