By Eric Schmitt and Julian E. Barnes

WASHINGTON — The Ukrainians say they need faster shipments of long-range artillery and other sophisticated weapons to blunt Russia’s steady advance. The United States and the Europeans insist more are on the way but are wary of sending too much equipment before Ukrainian soldiers can be trained. The Pentagon is concerned about potentially depleting its stockpiles in the coming months.

The Biden administration and its allies are struggling to balance their priorities against Kyiv’s demands as Russian forces intensify their bombardment of cities and villages across eastern Ukraine, according to American and other Western diplomats, military officials and lawmakers.

US officials say Ukraine could mount a counterattack and claw back some — though not all — of the territory it has lost if it can continue to exact a bloody toll on Russia until new weapons can flow in from the West. But some officials are concerned that pulling too many Ukrainian artillery specialists off the front lines for weeks of training on the new weapons could weaken Ukrainian defences, accelerate Russian gains and make any future counterattacks more difficult to carry out.

“There are no good choices in a situation like this,” said Sen. Jack Reed, D-RI, head of the Armed Services Committee. “You have to take your best artillery officers and enlisted personnel and send them back for a week or two of training. But in the long run, I think that’s probably the smarter move.”

In addition, Pentagon officials have expressed concerns about hurting US combat readiness if the war continues for months or longer. After two decades of mostly supporting counterterrorism missions, America’s defence industry largely stopped making the kinds of weapons Ukraine will need to survive a long war of attrition. The United States has authorized $54 billion in military, economic and humanitarian aid for Ukraine and has sent more than $7 billion in weapons drawn from existing Pentagon stockpiles.

Ukraine’s urgent requests come at a time when the United States appears to have reached the high end of the type of sophisticated arms it is providing. The next shipments are to include truck-mounted, multiple-rocket launchers called HIMARS, Harpoon anti-ship missiles and precision-guided Excalibur howitzer shells. But the fighter jets and advanced armed drones on Ukraine’s wish list have been shelved for now as either overly provocative to Moscow or too time-consuming for the Ukrainians to learn how to use.

The nearly five-month war is at a critical moment, US officials and others familiar with the intelligence assessments say. As many as 100 to 200 Ukrainian soldiers have died every day since Russia shifted its military campaign in the spring to focus on eastern Ukraine. But overall, about 20,000 Russians have been killed. Injuries have taken about 60,000 more off the battlefield. Nearly a third of Russia’s equipment has been destroyed in the war, according to Western officials, including several who spoke on the condition of anonymity to discuss sensitive information.

To replenish its military, Russia would have to mobilize more of its population, by making a declaration of war — officially the conflict remains a “special military operation” — or by moving troops and equipment from Russia’s Far North or Far East to Ukraine.

That President Vladimir Putin has been reluctant to undertake either move is a sign that he believes time is on his side, officials say. Instead, the Kremlin is trying to fill its manpower shortfall with a motley mix of Ukrainians from the separatist territories, mercenaries and militarized National Guard units, and by promising large cash bonuses for volunteers.

Putin might also think that Western support for Ukraine will soon reach its limit as Americans and Europeans grow more anxious about energy prices, which have spiked since the war began.

One sign of Putin’s current approach, according to people briefed on the assessments of the campaign, is that the Kremlin is no longer pressing for quick battlefield gains as it did in the early push to seize Kyiv, Ukraine’s capital. Putin has reshuffled his top battlefield commanders in Ukraine once again in recent weeks, and American officials say the Russians have switched to slow, grinding tactics that the Kremlin appears content to let play out.

The Russian military has relied heavily on its immense advantage in long-range artillery in eastern Ukraine’s Donbas region, pounding Ukrainian soldiers — as well as cities and towns — from a distance, before trying to move in.

In recent days, some Russian forces have reportedly taken a strategic pause, according to an assessment by the Institute for the Study of War, while others have started shelling towns in Donetsk, a territory in the Donbas.

Many of these Russian troops are slowing to rearm and reorganize after the brutal artillery duels in the Luhansk portion of the Donbas, while the Kremlin scrambles to fill its manpower shortages to continue the war.

“The Russians are literally scraping the bottom of the barrel for troops and replacement equipment,” said Frederick B. Hodges, a former top US Army commander in Europe who is now with the Centre for European Policy Analysis.

American officials say it will be difficult for Ukraine to mount a counteroffensive in the near term, but that it still has advantages. Throughout the war, the fight has largely favoured the defenders, who can inflict heavy casualties from well-protected positions. The Ukrainians have used modern American and European-designed weaponry, including the HIMARS and anti-tank missiles like Javelins and NLAWs, with deadly effectiveness against the Russians. But Russia’s superior firepower has allowed its battered forces to inch forward.

Key to Ukrainian survival and the further slowing of the Russian advance will be additional Western training and hardware.

The first group of Ukrainian soldiers arrived in Britain last week to attend a new program that officials there say will ultimately train as many as 10,000 Ukrainian recruits in weaponry, patrol tactics, first aid and other skills, the Britain’s defence secretary, Ben Wallace, recently said.

“The UK’s response to evolving Ukrainian requirements considers both the equipment needed to mount and maintain an effective response to Russian aggression and the training required to use the respective capability,” said Air Vice Marshal Mick Smeath, the British defence attaché in Washington.

US intelligence agencies have struggled to assess how quickly Ukrainian forces can absorb and employ sophisticated equipment. The HIMARS — for High Mobility Artillery Rocket System — are the centrepiece of a raft of new Western long-range weapons that the Ukrainian military is switching over to as its arsenal of Soviet-era howitzer and rocket ammunition dwindles.

The truck-mounted, multiple-rocket launchers fire satellite-guided rockets that have a range of more than 40 miles, greater than anything Ukraine had possessed. The first two batches are destroying Russian ammunition depots, air defences and command posts deep behind the front lines, American and Ukrainian officials said.

“HIMARS have already made a HUUUGE difference on the battlefield,” Ukraine’s defense minister, Oleksii Reznikov, said in a Twitter message over the weekend.

The White House said on Friday that it would send four more HIMARS from Pentagon stocks, joining the eight already on the ground in Ukraine with their American-trained crews of about 100 Ukrainian soldiers. Administration officials privately indicate that more will be sent. Britain and Germany have each pledged to supply three similar launchers.

Ukrainian officials, however, say they need as many as 300 multiple-rocket launchers to combat Russia, and some former Pentagon officials say at least 60 to 100 of the launchers are needed to disrupt the Russian offensive.

-New York Times