After holding back many of its units trained and armed by the West, Ukraine is now committing them, the officials said, but it remained unclear whether a full-scale assault was taking place.
Ukraine has launched the main thrust of its counteroffensive, throwing in thousands of troops held in reserve, many of them Western-trained and equipped, two Pentagon officials said on Wednesday, hours after Russian officials reported major Ukrainian attacks in the southern Zaporizhzhia region.
A spokesman for Russia’s Defense Ministry, Igor Konashenkov, said the Ukrainians had mounted a “massive” assault with three battalions, reinforced with tanks, south of the town of Orikhiv, and then another a few miles farther south near the village of Robotyne, according to the state news agency Tass. Both were repelled, the ministry said.
Other American officials cautioned that the latest Ukrainian attack might be preparatory operations for the main thrust or perhaps just reinforcements to replenish war-weary units.
The challenge for the Ukrainians, since they began their counteroffensive in early June, has been to blast open a gap in the deep Russian defense network, and then try to pour through a much larger force.
Speaking on the condition of anonymity to discuss internal deliberations, officials at the White House and Pentagon said on Wednesday that they were watching the increased activity with keen interest, and that Ukrainian officials had told them the new operation, if successful, would last one to three weeks.
“This is the big test,” said one senior official.
Administration officials and analysts said it might be only a matter of days to assess whether the attacks might be successful. “It will be clear soon whether this attack will allow Ukraine to change the current dynamic,” said Michael Kofman, a senior fellow at the Carnegie Endowment for International Peace.
Ukrainian officials declined to confirm that the assaults took place.
The force cited by the Kremlin — three battalions, roughly up to 3,000 troops — is relatively small. A Russian occupation official describing the attack referred on the Telegram app to Ukrainian “brigades,” and in a later post to “battalions,” a major difference. A brigade typically has three to five battalions.
The United States and other Western allies have trained about 63,000 Ukrainian troops, according to the Pentagon, and have supplied more than 150 modern battle tanks, a much larger number of older tanks, hundreds of infantry fighting vehicles and thousands of other armored vehicles. All of those figures continue to rise, and much of that manpower and gear had been held in reserve until now, as Ukrainian forces fought to find — or create — a strategic vulnerability they could exploit.
The American officials said most of the remaining reserves were now being committed.
In villages all along the southern front line on Wednesday, unusually heavy artillery fire could be heard as Ukrainian guns thundered from hidden positions and Russian artillery and mortars targeted former Russian positions and villages now occupied by Ukrainian soldiers. Ukrainian troops deployed along that part of the front say they are steadily pushing the Russian troops back in what they describe as step by step, rather than breakthrough, movements.
Since seizing Ukrainian territory in last year’s invasion, the Russians have built a dense defensive web of minefields, trenches, bunkers, tank traps and obstacles along a front line that curves and winds hundreds of miles through the Zaporizhzhia region in the south and the Donetsk and Luhansk regions to the east. That has made the counteroffensive slow going, frustrating both Ukrainians and their Western backers.
The area around Orikhiv is one of three main axes of the assault, and the westernmost one. Ukrainian leaders hope for a breakthrough to the town of Tokmak and then as far as the city of Melitopol, more than 50 miles south, near the Sea of Azov. Both are highway and railroad hubs, and driving a wedge that deep would effectively split the Russian-held territory in two, making resupply and coordination more difficult for Moscow’s forces.
Some of Ukraine’s newly trained and equipped brigades have been engaged in fighting there alongside long-established units of marines and mechanized infantry. The strength of Russian firepower and defenses has forced the Ukrainians to adjust their tactics, but before Wednesday they had broken through the first line of Russian defenses in some places, capturing a handful of settlements.
Vladimir Rogov, a Russian occupation official in the region, said on the Telegram app that fierce battles were waged on Wednesday south of Orikhiv, involving Western-trained Ukrainian troops equipped with “more than 100” armored vehicles, including an unspecified number of German-made Leopard tanks and American-made Bradley Fighting Vehicles.
The Ukrainian military’s general staff, in its daily update, said only that Russian forces were engaged in defensive operations in the Zaporizhzhia region. A spokesman for the general staff, Andriy Kovalev, said that Russian forces had unsuccessfully tried to restore lost positions northeast of Robotyne.
“The enemy continues to put up strong resistance, moves units and actively uses reserves,” he said.
President Volodymyr Zelensky of Ukraine said on Telegram that he had met with Gen. Valery Zaluzhny, the commander of the armed forces, and discussed offensive and defensive fighting on the front line, but he gave no specifics about military operations. “We believe in our boys,” he said. “We continue to work.”
But it is the Russians who are on the offensive in other contexts — at sea and in the air.
On Wednesday evening, Russia launched a large-scale and complex aerial bombardment of Ukraine, firing cruise and ballistic missiles at targets across the country, including the western city of Starokostiantyniv, far from the front, the Ukrainian Air Force said. Many of the missiles suddenly changed course during flight to evade Ukrainian air defenses, it said.
The Ukrainians said that Russian warplanes had fired 36 cruise missiles and four ballistic missiles, and that they had been able to shoot down 33 of the cruise missiles. It was unclear how much damage was done, and whether the barrage was tied to the offensive on ground.
Since July 17, when Russia withdrew from a deal allowing ships to carry exports of grain and other foodstuffs from Ukraine, it has repeatedly bombarded Ukrainian ports on the Black Sea, particularly facilities used to store and move grain. The Kremlin, whose navy dominates the Black Sea, has also said that any vessel moving to or from Ukraine would be treated as hostile.
Kyiv, in turn, has said it would step up its own naval attacks, and it has used maritime drones packed with explosives against Russian ships and infrastructure. The Russian military said on Tuesday that it had thwarted an attack on one of its warships by Ukrainian drones; the claim could not be independently confirmed.
The threats and escalations have raised fears of a clash at sea involving neutral shipping. The United States has warned that Russia might attack a civilian vessel and blame it on Ukraine.
The collapse of the grain deal is of worldwide interest, because it chokes off a significant fraction of the global food supply, particularly for parts of the Middle East and Africa. The United Nations Security Council met on Wednesday for the third time since then to discuss the matter, though with Russia holding veto power, no action was expected.
Britain’s military intelligence service said on Wednesday that the Russian fleet had taken a more aggressive posture to tighten its blockade against Ukraine. A modern Russian warship has been deployed to the shipping lanes linking Odesa, Ukraine’s biggest port, to Turkey, the destination for grain exports under the deal, and it could be part of a plan “to intercept commercial vessels.”
Eric Schmitt reported from Washington, Matthew Mpoke Bigg from London and Carlotta Gall from the Zaporizhzhia region of Ukraine. Reporting was contributed by Marc Santora from Kyiv, Ukraine, and Farnaz Fassihi from New York.