Stung by battle losses and massing troops for a brand new battle in jap Ukraine, Russia has warned the Biden administration to cease supplying superior weapons to Ukrainian forces or face “unpredictable penalties,” American officers mentioned Friday.

The Russian message — considered one of a sequence of warnings punctuated by a proper protest word, delivered on Tuesday — advised rising issues in Moscow that the weapons had been severely hindering Russia’s fight capabilities.

The existence of the message was disclosed because the Kremlin was funneling armaments, together with assault helicopters, to Russia’s border with jap Ukraine for the subsequent part of its two-month-old invasion of the nation.

Over the course of the battle, the U.S. administration has offered more and more heavier weapons to the Ukrainians — together with 155-mm howitzers — because the battle has ramped up, and it introduced a brand new $800 million arms package deal this week.

Again in February, because the battle started, the administration anxious such weaponry might unnecessarily provoke Russia. However after coming below strain from President Volodymyr Zelensky of Ukraine and members of Congress from each events, the administration has determined to supply a few of the sorts of heavy weapons it says Ukraine would require within the subsequent part of the battle.

The Russian warnings have come because the invasion has met unexpectedly stiff Ukrainian resistance and has uncovered weaknesses in Russia’s typical armed forces.

President Vladimir V. Putin of Russia has put in a brand new command to supervise the Ukraine battle and this previous week publicly advised for the primary time that Russia’s objectives had been restricted to securing the Donbas, the part of jap Ukraine bordering Russia the place Moscow-backed separatists have been combating for eight years.

Russia’s objectives when its army invaded on Feb. 24 appeared way more formidable, with plans to besiege and seize the capital, Kyiv, within the north, reducing off Mr. Zelensky’s authorities from the remainder of the previous Soviet republic, which Mr. Putin has mentioned he doesn’t even take into account a rustic.

That technique backfired and Russian forces retreated final month. In addition they have didn’t utterly seize the strategic southeast port of Mariupol regardless of relentless bombardments which have turned that after bustling metropolis of 450,000 right into a wasteland of dying and battle’s harmful horrors.

Pavlo Kyrylenko, the governor of the Donetsk area of Jap Ukraine, informed CNN on Friday that Ukrainian troops had been nonetheless in command of Mariupol, however that the town had been “wiped off the face of the earth by the Russian Federation, by those that won’t ever have the ability to restore it.”

In what seemed to be one other army embarrassment for Russia that it has sought to cowl up, a senior U.S. protection official mentioned Friday that Russia’s Black Sea flagship Moskva, a missile cruiser that sank Thursday, had been struck by two Ukrainian Neptune missiles, and never crippled by an unintentional hearth and explosion throughout a storm, because the Kremlin has asserted.

It was the primary American corroboration of Ukraine’s claims that its Neptune missiles — a newly deployed weapon with a 190-mile vary — had hit the ship, which was struck 65 miles south of the port of Odesa.

The lack of the Moskva was greater than only a humiliation, because it might now severely impair any Kremlin plans for an amphibious assault on Ukraine’s southern coast. The loss additionally raised questions on Russian dominance of Ukraine’s airspace and the obvious incapacity of the Moskva, a complicated warship, to evade or intercept the Neptunes with its personal protection techniques.

The U.S. official mentioned that American intelligence evaluation had indicated an unspecified variety of casualties, contradicting Russian claims that every one crew members had been safely evacuated.

The Russian diplomatic protest word, known as a démarche, was despatched by way of regular channels, two administration officers mentioned, and was not signed by Mr. Putin or different senior Russian officers. However it was an indicator, one administration official mentioned, that the weapons despatched by the USA had been having an impact.

American officers mentioned the tone of the word was according to a sequence of public Russian threats, together with to focus on deliveries of weapons as they moved throughout Ukrainian territory.

Officers mentioned the word didn’t immediate any particular concern contained in the White Home. However it has touched off a broader dialogue contained in the Pentagon and intelligence businesses about whether or not the “unpredictable penalties” might embody making an attempt to focus on or sabotage a few of the weapons shipments whereas nonetheless in NATO territory, earlier than they’re transferred to Ukrainians for the ultimate journey into the arms of Ukrainian troops. The supply of the protest word was first reported by The Washington Submit.

The weapons President Biden approved this week for switch to the Ukrainians embody long-range artillery that’s fitted to what American officers imagine will probably be a unique type of battle within the open areas of the Donbas, the place Russian forces seem like massing for an assault in coming days.

Pentagon officers had been insistent within the run-up to the battle that the USA present solely defensive weaponry that will keep away from escalation.

Jake Sullivan, the president’s nationwide safety adviser, described in an interview on the Washington Financial Membership on Thursday how he and Gen. Mark A. Milley, the chairman of the Joint Chiefs of Employees, had reviewed weapons requests. They went over every merchandise with their Ukrainian counterparts, speaking about what the USA had in its shares and what it might ship shortly.

Studies by pro-Kremlin media have highlighted antitank techniques and different Western weapons utilized by Ukrainian forces, selling the concept that Russia shouldn’t be at battle with Ukraine however with an American-led alliance looking for to destroy Russia. Mr. Biden and his aides have denied that, saying that they wished to keep away from direct battle with Russia and had little interest in American-engineered regime change.

In Moscow, commentators have been more and more calling on Russia to strike Ukrainian roads and railroads to inhibit the weapons transfers. Whereas Russia has focused lots of Ukraine’s airports, the nation’s floor transportation community stays largely intact.

“The time has come to not communicate, however to assault,” Viktor Baranets, a army columnist for Komsomolskaya Pravda, Russia’s greatest tabloid, mentioned on Friday. “Prepare echelons should be destroyed together with the railways.”

Russia’s concern could partly be over the accuracy Ukraine confirmed in hitting the Moskva, considered one of its most subtle warships.

The Russian démarche echoed the general public rhetoric of officers in Moscow, who’ve been warning for weeks that Western arms deliveries to Ukraine would delay the battle and be met with a tricky response.

It got here as the extent of concern amongst Russian officers over the impression of Western arms has been growing, mentioned Andrei Kortunov, the director common of the Russian Worldwide Affairs Council, a analysis group near the Kremlin.

“It appears the USA and the West generally are proper now testing the bounds of Russian tolerance relating to weapons deliveries,” Mr. Kortunov mentioned. “It’s clear that these volumes are already so important that they’ll have an effect on the course of the hostilities, and that is elevating issues.”

A Russian deputy international minister, Sergei A. Ryabkov, mentioned on Friday that Russia was “making it clear to the Individuals and different Westerners” that makes an attempt to hamper what Russia is asking its “particular army operation” in Ukraine and improve Russian losses could be “curbed in a tricky method.”

He added that NATO automobiles carrying weapons throughout Ukrainian territory could be “seen by us as legit army targets.” His feedback got here in an interview with Tass, the state-run information company.

NATO arms off weapons to the Ukrainians in ways in which search to keep away from having the alliance’s automobiles traverse Ukrainian soil. However Mr. Ryabkov’s feedback have heightened issues about whether or not Russia would take the chance of putting inside NATO territory.

When Mr. Putin introduced his “particular army operation” on Feb. 24, he mentioned that these “who could also be tempted to intrude” in Ukraine would face penalties as extreme “as you will have by no means seen in your total historical past.”

“Regardless of how the occasions unfold, we’re prepared,” Mr. Putin mentioned on the time. “All the required choices on this regard have been taken.”

However Russia has thus far appeared cautious to not escalate the battle in a approach that would draw NATO international locations extra instantly — for example, not putting weapons convoys crossing into Ukraine from Poland.

“There are nonetheless fears relating to strikes which will hit the territory of NATO member international locations,” Mr. Kortunov mentioned. “One definitely doesn’t wish to create a pretext for some additional escalation.”

David E. Sanger and Helene Cooper reported from Washington, and Anton Troianovski from Istanbul. Reporting was contributed by Marc Santora from Krakow, Poland; Michael Schwirtz from Lviv, Ukraine; and Julian E. Barnes and Eric Schmitt from Washington.