Russia said the West was playing with fire by considering allowing Ukraine to strike deep into Russia with Western missiles and cautioned the United States on Tuesday that World War Three would not be confined to Europe.

Ukraine attacked Russia's western Kursk region on Aug. 6 and has carved out a slice of territory in the biggest foreign attack on Russia since World War Two. President Vladimir Putin said there would be a worthy response from Russia to the attack.

Sergei Lavrov, who has served as Putin's foreign minister for more than 20 years, said that the West was seeking to escalate the Ukraine war and was "asking for trouble" by considering Ukrainian requests to loosen curbs on using foreign-supplied weapons.

Since invading Ukraine in 2022, Putin has repeatedly warned of the risk of a much broader war involving the world's biggest nuclear powers, though he has said Russia does not want a conflict with the U.S.-led NATO alliance.

"We are now confirming once again that playing with fire - and they are like small children playing with matches - is a very dangerous thing for grown-up uncles and aunts who are entrusted with nuclear weapons in one or another Western country," Lavrov told reporters in Moscow.

"Americans unequivocally associate conversations about Third World War as something that, God forbid, if it happens, will affect Europe exclusively," Lavrov said.

Lavrov added that Russia was "clarifying" its nuclear doctrine.

Russia's 2020 nuclear doctrine sets out when its president would consider using a nuclear weapon: broadly as a response to an attack using nuclear or other weapons of mass destruction or conventional weapons "when the very existence of the state is put under threat".