As Russian airstrikes cut water and power and expanded its campaign to drive Ukraine into the cold and dark, the Pentagon looked ahead to increasingly difficult battlefield conditions for both sides during the winter months.
Watch the briefing in the player above.
It said weather would be a significant factor in ongoing military operations in Ukraine.
"I think that when you look at things like rain, snow, mud, the impact that it has on the terrain, it definitely will add another level of complexity to an already very dynamic battlefield," said Pentagon Spokesman Brig. Gen. Pat Ryder.
Earlier, Ukrainian President Volodymyr Zelenskyy said nearly one-third of Ukraine's power stations have been destroyed in the past week, "causing massive blackouts across the country."
Depriving people of water, electricity and heat as winter begins to bite and the broadening use of so-called suicide drones that nosedive into targets have opened a new phase in Russian President Vladimir Putin's war.
On Tuesday, U.S. Defense Secretary Lloyd Austin met behind closed doors with Ben Wallace, his British counterpart.
EXPLAINER: How Russia is using Iranian killer drones to spread terror in Ukraine
Ryder said the two men are talking about how to continue to aid Ukraine in its fight against Moscow.
"Our focus will continue to be on working with them to identify what their needs are, to include things like air defense. And we'll work to try to get those capabilities to them as quickly as possible," Ryder said.
The latest city shorn of power was Zhytomyr, home to military bases, industries and leafy boulevards, about 140 kilometers (85 miles) west of Kyiv.
In the capital of Kyiv, missile strikes damaged two power facilities and killed two people, city authorities said. The attack left 50,000 people without power for a few hours, the facilities' operator said.
In the past week alone, more than 100 self-destructing Iranian-made drones have slammed into power plants, sewage treatment plants, residential buildings, bridges and other targets in urban areas, Ukraine's Foreign Ministry said.
In a televised address on Monday night, Zelenskyy said Russia is using the drones because it is losing ground in the war.