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CNN  — 

Russian forces have made some progress in Moscow’s renewed assault on eastern Ukraine, according to US and NATO officials, as their military tries to fix the myriad problems that plagued the early weeks of the invasion.

The US has seen “some evidence” of improvement in Russia’s ability to combine air and ground operations, as well as its capacity for resupplying forces in the field, officials say.

The progress is “slow and uneven,” a senior US defense official said, allowing Russian forces to advance only “several kilometers or so” each day.

But the US assesses that Russia is trying to learn from the mistakes it made early on, where columns of tanks and armor ran out of food and fuel, leaving them easy prey to Ukrainian hit-and-run tactics.

Russia has placed command and control elements near its border with eastern Ukraine, according to a senior NATO official, a sign they are attempting to fix the communications and coordination failures observed in the attack on Kyiv.

Before the invasion began on February 24, Russia amassed 125 to 130 battalion tactical groups, known as BTGs, around Ukraine and near Kyiv in particular, but when the fighting began, Russia’s military leaders showed little ability to have them fight as one.

There are 92 BTGS in country now, with another 20 just across border in Russia, according to the senior defense official.

“The attacks are somewhat better coordinated but with small formations. Company size units with helicopter support,” a European defense official said. “The lowest level of mutual support. In NATO this would be basic stuff.”

Still, western officials familiar with the latest intelligence say even if Russia has learned key lessons from its systemic failures in the first stage of the conflict, it’s not clear that Moscow will be able to implement the necessary changes to dominate in the Donbas region.

Its military has suffered heavy losses in both manpower and equipmen