General Mark Milley, Chairman of the US Joint Chiefs of Staff, has estimated that around 100,000 Russian and 100,000 Ukrainian soldiers have been killed or injured since Moscow waged its ongoing war against Kiev on February 24.
Addressing an event in New York late Thursday, the most senior US general also said that around 40,000 civilians had died in the war, reports the BBC.
These are the highest-ever estimates offered by a Western official.
General Milley, who serves as US President Joe Biden's most senior military adviser, added that for any talks to be successful, both Russia and Ukraine would have to reach a "mutual recognition" that a wartime victory "is maybe not achievable through military means, and therefore you need to turn to other means".
He added that the scale of the casualties could convince both Moscow and Kiev of the need to negotiate over the coming winter months, when fighting may slow due to freezing conditions.
"You're looking at well over 100,000 Russian soldiers killed and wounded... Same thing probably on the Ukrainian side," the BBC quoted General Milley as saying.
"There has been a tremendous amount of suffering, human suffering," he said.
While Moscow's latest update in September said that just 5,937 troops had been killed since the start of the war, Ukraine has largely refrained from giving casualty figures.
In August, the armed forces' commander-in-chief, Valeriy Zaluzhniy, was quoted in Ukrainian media saying 9,000 Ukrainian soldiers had died so far.
The American General also also noted that between 15 and 30 million refugees have been created since Russia launched its invasion.
The UN has recorded 7.8 million people as refugees from Ukraine across Europe, including Russia. (SJ/IANS)