Media reports say America's top general estimated on November 9 that Russia's military had seen more than 100,000 of its soldiers killed and wounded in Ukraine, and added Ukraine’s armed forces "probably" suffered a similar level of casualties in the war.

Remarks by General Mark Milley, Chief of the Joint Chiefs of Staff of the U.S. Army, offer the highest US estimate of casualties to date in the nearly nine-month-old conflict, and came as Ukraine and Russia face a potential winter lull in fighting that analysts say could offer an opportunity for some kind of negotiations.

Asked about prospects for diplomacy in Ukraine, Milley noted the early refusal to negotiate in World War I compounded human suffering and led to millions more casualties.

“So when there’s an opportunity to negotiate, when peace can be achieved … seize the moment,” Milley told the Economic Club of New York.

Earlier on Wednesday, Russia announced its troops would withdraw from the west bank of the Dnepr River near the strategic southern Ukrainian city of Kherson – in a significant setback for Moscow and potential turning point in the war.

Al Jazeera says Milley and Ukrainian President Vladimir Zelenskiy refrained from overplaying the significance of Moscow’s retreat from Kherson, even as US President Joe Biden suggested it was evidence that eight months into the war Russia has “real problems” on the battlefield.

Zelenskiy has suggested Russia could be strategically feigning a pullback.

“The enemy does not bring us gifts, does not make ‘gestures of goodwill’,” Zelenskiy said, adding any gains by Ukraine come at the expense of “lives lost by our heroes”, according to Al-Jazeera.

Milley said initial indicators suggest Russia was following through with its withdrawal from Kherson.  But he cautioned it could take time to complete.

Milley said the conflict so far had turned anywhere from 15 million to 30 million Ukrainians into refugees, and killed probably 40,000 Ukrainian civilians.

The United States and its NATO allies have reportedly stopped short of direct intervention in Ukraine, but are arming, advising, and enabling its military to defend Kiev against Russia’s invading armies.