Watch Ukrainian troops fire US-supplied M777 Howitzers on Russian positions
02:12 - Source: CNN
CNN  — 

Russian forces are gaining an advantage in eastern Ukraine as they learn from mistakes made during the earlier stages of their invasion of the country, including better coordinating air and ground attacks and improving logistics and supply lines, two US officials with direct knowledge of US intelligence assessments told CNN.

The US does not expect new weapons systems recently supplied to Ukrainian forces, including the HIMARS multiple rocket launch system, to immediately change the situation on the battlefield in part because those systems are so far being sent with both a limited range and a limited number of rockets to ensure they are not fired into Russian territory. Additionally, Russian forces have been able to destroy some of the new Western-supplied weapons, including M777 howitzers, in targeted attacks.

A man walks past the wreckage of a car in Lysychansk on June 21, 2022, as Ukraine says Russian shelling has caused "catastrophic destruction" in the eastern industrial city.

The US assessments, which increasingly envision a long and punishing battle in eastern Ukraine, come as the months-long war there has reached a pivotal moment in recent days. Ukraine’s military has been burning through Soviet-era ammunition that fits older systems, and Western governments are facing a tough decision on whether they want to continue increasing their assistance to the country.

The US assessments paint a dismal image of the future of the war, with high personnel and equipment losses on both sides. US officials believe that Russian forces plan to maintain intense attacks in the east, characterized by heavy artillery and missile strikes, with the intention of wearing down Ukrainian forces and NATO resolve over time.

Russia’s advancements were brought into plain view in recent days after Ukraine’s defense of Lysychansk – the last city in the Luhansk region it still holds – became a lot more tenuous. In the last couple of days, Russians have advanced into several villages south of Lysychansk, though not without sustaining losses from Ukrainian artillery fire.

In the coming weeks, Ukrainian President Volodymyr Zelensky will virtually address the upcoming G7 and NATO summits, senior US administration officials have said, with the leader looking to shore up Western support for his country. During the G7, President Joe Biden will unveil steps alongside other leaders to increase pressure on Russia for its invasion. And at NATO, the US will announce measures to “strengthen European security, alongside expected major new contributions from allies,” one official said.

Members of the Ukrainian parliament have told US lawmakers that the Russian military has calculated how much ammunition Western allies have in stockpiles for the Ukrainian military’s mostly Russian-made artillery – and plan to wait for Ukrainian forces to run out over time.

“Putin is not deterred and I don’t think he will ever be deterred,” Rep. Mike Quigley, a Democrat from Illinois who sits on the House Intelligence Committee, told CNN.

“This war could last years,” he added.

At home, US and NATO partners are beginning to see the limits of their own supplies of certain advanced weapons, including shoulder-fired anti-aircraft missiles and Javelin anti-tank missiles. These weapons systems have their own complicated supply lines, meaning it could take years to replace the thousands of such missiles already supplied to Ukrainian forces.

Meanwhile, the US Defense Department’s watchdog has opened an evaluation of the department’s plans to restock its own munitions and equipment stockpiles as it continues to supply significant quantities to Ukraine, the agency announced Wednesday.

“The objective of this evaluation is to determine the extent to which the DOD has planned to restock its equipment and munitions provided to Ukraine,” the department’s inspector general said in a statement.

CNN’s Devan Cole, Katie Bo Lillis, Barbara Starr, Natasha Bertrand, Oren Liebermann, Tim Lister, Donald Judd and Kevin Liptak contributed to this report.