Troops are withdrawing from the besieged city of Avdiivka in eastern Ukraine, the Ukrainian armed forces said on Friday.

Col. Gen. Alexander Sirsky, Ukraine’s commander-in-chief, said troops were withdrawing to “save the lives and health of soldiers” and to move to a more favorable position.

“Our soldiers fulfilled their military duty duly, did their best to destroy the best Russian military units, inflicted significant losses in manpower and equipment to the enemy,” Sirsky said in a statement. “We use measures to stabilize the situation and maintain occupied positions. The life of military is the highest value.”

Avdiivka has become a key battleground in the war in the past few months as Russian forces have assaulted the position as part of an overall strategy to take the rest of the Donetsk region in Ukraine.

The White House warned earlier this week that Russian forces were close to taking the city as Ukrainian soldiers struggle with limited reserves and depleting ammunition. The last of the U.S. military aid for Ukraine ran out at the end of last year, and Congress has yet to approve a new package.

A senior U.S. defense official told reporters Friday that Ukraine faces challenges across the entire front from Russian offensives if more aid is not approved.

“We see this as something that could be the harbinger of what is to come if we do not get this supplemental funding,” the official said of Avdiivka.

But Russian forces began assaulting the town more heavily in October after a Ukrainian counteroffensive began to slow down, which ultimately failed to overcome Russian positions.

The town is located in the center of Donetsk, which Russia is trying to seize full control of along with the remaining portions of the Luhansk region it does not control. Russia currently holds about 18 percent of Ukraine in the eastern and southeastern regions.

While Avdiivka alone does not give Russia a major advantage, it could help Moscow launch more offensives toward the rest of Donetsk. Ukraine has defended its positions vigorously in Avdiivka, including in an embattled coke and chemical plant near the town.

The withdrawal is likely to give Moscow another symbolic victory, with the town falling after the city of Bakhmut fell last spring and after Russia’s successful defense against the Ukrainian counteroffensive. 

With the battlefield shifting in his favor and crucial Western aid to Ukraine in doubt, Russian President Vladimir Putin has shown a more optimistic and public face in the past few months, including doing a major sit-down with former Fox News host Tucker Carlson in Moscow.

Still, Russia has lost a considerable number of forces in the war, with some 315,000 killed or wounded, according to the latest U.S. estimates. Ukraine has damaged the Russian fleet on the Black Sea, forcing them to withdraw from the historic headquarters in Crimea.

The Biden administration still warned that without another aid package, Ukraine faces steep challenges against a larger Russian army supported by a boosted defense industry.

Updated at 8:35 pm EST.