The U.S. President said that sending American troops to Ukraine could lead to a world war.

President Joe Biden urged American citizens to leave Ukraine immediately and warned of a potential major conflict with Moscow if American and Russian troops engage each other on Ukrainian soil.

“American citizens should leave, they should leave now,” Biden said in an interview with NBC News.

“We are dealing with one of the largest armies in the world. This is a completely different situation, and everything can change very quickly,” the president said, referring to the Russian armed forces.

Biden also confirmed that under no circumstances would he send troops to Ukraine, even to rescue Americans in the event of a Russian invasion.

“It would become a world war. When the Americans and Russians start shooting at each other, we will find ourselves in a completely different world,” the U.S. president warned.

Western leaders are engaged in “shuttle diplomacy” to calm the shattered nerves in both Russia and Ukraine. However, Biden’s comments, as well as a message from the Department of State – the diplomatic department on Thursday called on all U.S. citizens to leave Ukraine immediately – will almost certainly only inflame tensions.

However, Biden rejected the possible scenario of saving Americans in Ukraine with the help of the Pentagon, saying: “How are you going to search for them [Americans] at all?”

“I hope that even if Vladimir Putin

 had the stupidity to get involved in this, he is smart enough not to actually do anything that could negatively affect American citizens,” Biden said, adding that he was confident that he would not have to tell the Russian president personally about it, stressing: “He [Putin] knows about it.”