Russian reservists attend a ceremony before deployment to military units, in Rostov region
Russian reservists recruited during the partial mobilisation of troops attend a ceremony before departing to the zone of Russia-Ukraine conflict, in the Rostov region, Russia October 31, 2022. Reuters

There are conflicting views in Russia on whether or not to launch a renewed offensive in Ukraine, a senior U.S. State Department official said on Tuesday, reiterating that Washington would keep backing Kyiv regardless of which scenario plays out.

The 10-month-old conflict prompted by Russia's invasion of Ukraine has spiraled into the largest in Europe since World War Two, and has killed tens of thousands of people, driven millions from their homes and reduced cities to ruins.

But Russia's invasion has faltered badly since the summer with a string of losses to a Ukrainian counteroffensive that retook swaths of occupied territory and forced Moscow into a partial mobilization of 300,000 more troops.

"Certainly, there are some (within Russia) who I think would want to pursue (new) offensives in Ukraine. There are others who have real questions about the capacity for Russia to actually do that," the State Department official, speaking on the condition of anonymity, told reporters in Washington.

Russia is suffering "significant" shortages of ammunition, posing a serious problem along the war's front lines, the official said, and those that Moscow has called up to join its combat forces were often not "cohesive" units.

"There are all sorts of things that the Russians are dealing with in terms of having the necessary equipment, having the necessary ammunition that put some constraints on what they may want to do," the official said.

"At the same time, it's a very large machine."

Ukraine's top general, Valery Zaluzhniy, told The Economist last week Russia was preparing 200,000 fresh troops for a major offensive that could come from the east, south or even Belarus to the north as early as January, but more likely in spring.

Russian President Vladimir Putin visited Belarus on Monday, his first visit to the country since 2019, raising fears in Kyiv that he intends to pressure Moscow's fellow former Soviet ally to open a new invasion front against Ukraine.

The United States has demonstrated that it can quickly adapt its assistance to Ukraine as the nature of the battle changes, the official said, and would do the same in the event of a renewed offensive.

"If necessary, we'll respond. We're also working right now to make sure that the Ukrainians have what they would need to deal with that," he said.

Ukrainians, the official added, show no intention of slowing down either, and said they want to continue to press to take back more of the territory that was seized from them.

"I think the Russians have to factor that in."

On Tuesday, Ukraine's defense minister, Oleksii Reznikov, said Russia could prepare an attack force in Belarus to launch a new offensive on Ukraine, but that he hoped Minsk's troops wouldn't take part.

Russian forces used Belarus as a launchpad for an abortive attack on Kyiv in February, but Minsk has not joined the war directly or sent its own troops into battle in Ukraine.