AP — Russian air defenses shot down 31 Ukrainian drones during a concerted nighttime attack by Kyiv’s forces on border regions, the Russian Defense Ministry said Wednesday, as uncertainty grew over Ukraine’s future access to weapons and ammunition from its Western allies.

The drone attack appeared to be Kyiv´s largest single cross-border drone assault reported by Moscow since it launched its invasion 20 months ago. There were no immediate reports of any damage or casualties.

Ukraine is pressing on with a slow-moving counteroffensive it launched three months ago to expel Russian invaders, though mounting concerns about replenishing its military stocks and cracks in the Western wall of support cast a cloud over its efforts.

Adm. Rob Bauer, the head of NATO´s Military Committee, sounded the alarm about depleted stockpiles.

“The bottom of the barrel is now visible,” Bauer said of weapons systems and ammunition supplies.

With the war of attrition likely continuing through winter into next year, Bauer urged the defense industry to boost production “at a much higher tempo. And we need large volumes,” he told the Warsaw Security Forum, an annual two-day conference that continued Wednesday.

The Russian Defense Ministry didn´t provide any evidence for its claims about intercepting Ukrainian drones nor any details about any damage or casualties.

It also said Russian aircraft thwarted a Ukrainian attempt to deploy a group of soldiers by sea to the western side of Russian-annexed Crimea. The force attempted to land on Cape Tarkhankut, on Crimea´s western end, using a high-speed boat and three jet skis, the ministry said.

Moscow´s claims could not be independently verified, and Ukrainian officials made no immediate comment.

The Crimean Peninsula, which Russia illegally annexed from Ukraine in 2014, has been a frequent target of Ukrainian attacks. The region has been the key hub supporting the invasion.

Bauer´s stark warning on depleted weapons stockpiles adds to mounting concerns over the resupply of Ukraine´s armed forces, which has deepened amid political turmoil in the United States and the unprecedented and dramatic ouster Tuesday of House Speaker Kevin McCarthy.

The U.S. is by far Ukraine´s largest military supplier, but a faction in the House Republican majority, and many GOP voters, oppose sending more military aid to Ukraine.

The Pentagon has warned Congress that it is running low on money to replace weapons the U.S. has sent to Ukraine.

Mykhailo Podolyak, an adviser to Ukrainian President Volodymyr Zelenskyy, publicly questioned the motives of what he called “Western conservative elites.”

“Why are you so insistently against … destroying the Russian army, which has been terrifying,” he wrote on X, formerly Twitter.

The funding concerns prompted U.S. President Joe Biden to hold a phone call Tuesday with key allies in Europe, as well as the leaders of Canada and Japan, to coordinate support for Ukraine.

The call was held three days after Biden signed legislation hastily sent to him by Congress that kept the federal government funded but left off billions in funding for Ukraine´s war effort that the White House had vigorously backed.

Meanwhile Wednesday, sirens blared across Russia and television station briefly interrupted regular broadcasts to air emergency warnings as part of nationwide drills that started on the previous day to test the readiness of the country´s emergency agencies.

Russian media said that the scenario of the drills envisioned the increasing danger of a conflict between nuclear powers and simulated action in response to a situation in which 70% of housing and all vital infrastructure are destroyed and wide areas are contaminated by a radioactive fallout.

The drills follow a series of warnings from Russian officials that Western support for Ukraine has increased the threat of a direct military conflict between Russia and NATO.