Ukraine’s grinding counteroffensive is struggling to break through entrenched Russian defenses in large part because it has too many troops, including some of its best combat units, in the wrong places, American and other Western officials say.

The main goal of the counteroffensive is to cut off Russian supply lines in southern Ukraine by severing the so-called land bridge between Russia and the occupied Crimean Peninsula. But instead of focusing on that, Ukrainian commanders have divided troops and firepower roughly equally between the east and the south, the U.S. officials said.

As a result, more Ukrainian forces are near Bakhmut and other cities in the east than are near Melitopol and Zaporizhzhia in the south, both far more strategically significant fronts, officials say.

American planners have advised Ukraine to concentrate on the front driving toward Melitopol, Kyiv’s top priority, and on punching through Russian minefields and other defenses, even if the Ukrainians lose more soldiers and equipment in the process.

Only with a change of tactics and a dramatic move can the tempo of the counteroffensive change, said one U.S. official, who like the other half a dozen Western officials interviewed for this article spoke on the condition of anonymity to discuss internal deliberations.

Another U.S. official said the Ukrainians were too spread out and needed to consolidate their combat power in one place.

Nearly three months into the counteroffensive, the Ukrainians may be taking the advice to heart, especially as casualties continue to mount and Russia still holds an edge in troops and equipment.

In a video teleconference on Aug. 10, Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff; his British counterpart, Adm. Sir Tony Radakin; and Gen. Christopher Cavoli, the top U.S. commander in Europe, urged Ukraine’s most senior military commander, Gen. Valeriy Zaluzhnyi, to focus on one main front. And, according to two officials briefed on the call, General Zaluzhnyi agreed.

Admiral Radakin’s role has been especially important and not widely appreciated until now, the officials said. General Milley speaks to General Zaluzhnyi every week or so about strategy and Ukrainian military needs. But the Biden administration has prohibited senior U.S. officers from visiting Ukraine for security reasons and to avoid increasing tensions with Moscow. Britain, however, has imposed no such constraints, and Admiral Radakin, a polished officer who served three tours in Iraq, has developed close ties with his Ukrainian counterpart during multiple trips to the country.

American officials say there are indications that Ukraine has started to shift some of its more seasoned combat forces from the east to the south. But even the most experienced units have been reconstituted a number of times after taking heavy casualties. These units rely on a shrinking cadre of senior commanders. Some platoons are mostly staffed by soldiers who have been wounded and returned to fight.

Ukraine has penetrated at least one layer of Russian defenses in the south in recent days and is increasing the pressure, U.S. and Ukrainian officials said. It is close to taking control of Robotyne, a village in the south that is near the next line of Russian defenses. Taking the village, American officials said, would be a good sign.

A spokesman for the Ukrainian military did not respond to text messages or phone calls on Tuesday.

But some analysts say the progress may be too little too late. The fighting is taking place on mostly flat, unforgiving terrain, which favors the defenders. The Russians are battling from concealed positions that Ukrainian soldiers often see only when they are feet away. Hours after Ukrainians clear a field of mines, the Russians sometimes fire another rocket that disperses more of them at the same location.

Under American war doctrine, there is always a main effort to ensure that maximum resources go to a single front, even if supporting forces are fighting in other areas to hedge against failure or spread-out enemy defenses.

But Ukraine and Russia fight under old Soviet Communist doctrine, which seeks to minimize rivalries among factions of the army by providing equal amounts of manpower and equipment across commands. Both armies have failed to prioritize their most important objectives, officials say.

Ukraine’s continued focus on Bakhmut, the scene of one of the bloodiest battles of the war, has perplexed U.S. intelligence and military officials. Ukraine has invested huge amounts of resources in defending the surrounding Donbas region, and Ukraine’s president, Volodymyr Zelensky, does not want to appear as though he is giving up on trying to retake lost territory. But U.S. officials say politics must, at least temporarily, take a back seat to sound military strategy.

American strategists say that keeping a small force near the destroyed city is justified to pin down Russian troops and prevent them from using it as a base for attack. But Ukraine has enough troops there to try to retake the area, a move that U.S. officials say would lead to large numbers of losses for little strategic gain.

American officials have told Ukrainian leaders that they can secure the land around Bakhmut with far fewer troops and should reallocate forces to targets in the south.

Ukrainian leaders have defended their strategy and distribution of forces, saying they are fighting effectively in both the east and the south. The large number of troops is necessary to pressure Bakhmut and to defend against concerted Russian attacks in the country’s northeast, they say. Ukrainian commanders are competing for resources and have their own ideas of where they can succeed.

American officials’ criticisms of Ukraine’s counteroffensive are often cast through the lens of a generation of military officers who have never experienced a war of this scale and intensity.

Moreover, American war doctrine has never been tested in an environment like Ukraine’s, where Russian electronic warfare jams communications and GPS, and neither military has been able to achieve air superiority.

American officials said Ukraine has another month to six weeks before rainy conditions force a pause in the counteroffensive. Already in August, Ukraine has postponed at least one offensive drive because of rain.

“Terrain conditions are always fundamental drivers” of military operations, General Milley said in an interview with reporters on Sunday. “Fall and spring are not optimal for combined arms operations.”

Wet weather will not stop the fighting, but if Ukraine breaks through Russian lines in the coming weeks, the mud could make it more difficult to capitalize on that success and quickly seize a wide swath of territory, officials said.

More important than the weather, some analysts say, is that Ukraine’s main assault forces may run out of steam by mid- to late September. About a month ago, Ukraine rotated in a second wave of troops to replace an initial force that failed to break through Russian defenses.

Ukraine also shifted its battlefield tactics then, returning to its old ways of wearing down Russian forces with artillery and long-range missiles instead of plunging into minefields under fire. In recent days, Ukraine has started tapping into its last strategic reserves — air mobile brigades intended to exploit any breakthrough. While fighting could continue for months, U.S. and other Western officials say Ukraine’s counteroffensive would not have enough decisive firepower to reclaim much of the 20 percent of the country that Russia occupies.

U.S. officials say they do not believe the counteroffensive is doomed to failure but acknowledge that the Ukrainians have not had the success that they or their allies hoped for when the push began.

“We do not assess that the conflict is a stalemate,” Jake Sullivan, the White House’s national security adviser, said on Tuesday. “We continue to support Ukraine in its effort to take territory as part of this counteroffensive, and we are seeing it continue to take territory on a methodical systematic basis.”

While a smaller, dug-in Russian force has performed better in the south than American officials and analysts anticipated, the Kremlin still has systemic problems. Russian troops suffer from poor supply lines, low morale and bad logistics, a senior U.S. military official said.

But Russia is keeping with its traditional way of fighting land wars in Europe: performing poorly in the opening months or years before adapting and persevering as the fighting drags on.

By contrast, Ukrainian troops, in launching the counteroffensive, have the steeper hill to climb, the official said. It took them more than two months — rather than the week or so that officials initially thought — to get through the initial Russian defenses.

Several U.S. officials said they expect Ukraine to make it about halfway to the Sea of Azov by winter, when cold weather may dictate another pause in the fighting. The senior U.S. official said that would be a “partial success.” Some analysts say the counteroffensive will fall short of even that more limited goal.

Even if the counteroffensive fails to reach the coast, officials and analysts say if it can make it far enough to put the coastal road within range of Ukrainian artillery and other strikes, it could cause even more problems for Russian forces in the south who depend on that route for supplies.

Speaking to reporters on a flight to Rome on Sunday, General Milley said the past two months of the counteroffensive have been “long, bloody and slow.”

“It’s taken longer than Ukraine had planned,” he said. “But they are making limited progress.”

Zolan Kanno-Youngs contributed reporting.