The war in Ukraine could soon enter a new, even more dangerous phase. Russia, angry over the loss of its Black Sea Fleet flagship, has warned of “unpredictable consequences” if the US continues supplying weapons to Ukraine, while Ukraine’s President Volodymyr Zelensky struck a somber note telling CNN the world should be prepared for the possibility that Russian President Vladimir Putin could use tactical nuclear weapons. The sinking of the guided-missile cruiser Moskva on Thursday is the biggest wartime loss of a naval ship in 40 years – and a huge embarrassment for Russia. It comes at a time when US intelligence officials are warning about Putin’s increasingly unpredictable behavior and willingness to take risks due to his anger over Russia’s failures in Ukraine. While Moscow has denied the Ukrainian version of events – that the Moskva sunk after being struck by Ukrainian missiles – it was nevertheless forced to admit the ship went down. Russia has insisted the reason for the sinking was a fire, but the US on Friday confirmed Ukraine’s account, with a senior defense official saying that the US believes that two Ukrainian Neptune missiles hit the Russian warship. As the flagship of Russia’s Black Sea fleet, the Moskva was one of its most visible assets in the Ukraine war and its loss could impact the morale of Russian troops. Tellingly, the Russian government has not acknowledged casualties in the sinking of the ship, a marked contrast to the very public discussion about the Kursk submarine disaster, which claimed the lives of 118 sailors in 2000. Russia may have extinguished independent media, but the loss of the Moskva has likely made Putin even more furious about the situation in Ukraine. US officials believe Putin is angry over the failures of his troops in Ukraine. They believe Putin’s advisers have not been telling him the full truth and did not prepare him for potential setbacks. The warship fiasco comes just weeks after top Russian military officials announced a shift in the focus of the invasion after their offensive appeared to have stalled around major Ukrainian cities such as Kyiv and Kharkiv. Russia has also failed to achieve complete air superiority in Ukraine and has suffered heavy losses of personnel since the start of the invasion. Russia was quick to strike back. Ukraine’s Operational Command South said in a statement early Saturday that the situation in Ukraine’s southern Mykolaiv and Kherson regions was “increasingly hostile.” “Desperately trying to gain a foothold and hold on to the positions of the southern front, the world’s most shameful army is pursuing civilians in Mykolayiv and Kherson regions. The work of snipers has been recorded in some areas.” The statement said Russian forces were “enraged by the losses in the Black Sea” and had “intensified the missile threat” in the region. Natalia Humeniuk, the spokeswoman for the armed forces in southern Ukraine, said that the missile attacks since Thursday night were in retaliation for the Moskva sinking. “We all realize that we will not be forgiven,” she said, accusing Russia of using “cluster munitions prohibited by international conventions.” The UN Human Rights Monitoring Mission in Ukraine has previously said it had received credible allegations that Russian armed forces have used cluster munitions in populated areas in Ukraine. The nongovernmental organization Human Rights Watch (HRW) has also confirmed Russia’s use of cluster munitions throughout the conflict. Zelensky has on Friday praised the Ukrainian armed forces for repelling Russian attacks, saying they were “doing it brilliantly.” Zelensky has also praised the help Ukraine was getting from western countries, but has asked for more weapons to be shipped to the country. “The more and the sooner we get all the weapons we have requested, the stronger our position will be and the sooner peace will come,” he said. More weapons for Ukraine In another sign that the war in Ukraine is not going the way Russia has planned, Moscow has formally protested America’s ongoing shipment of weapons to Ukraine. It sent a diplomatic note to the State Department warning of “unpredictable consequences” should the support continue, according to two US officials and another source familiar with the document. Some Biden administration officials believe that the diplomatic note shows the Russians are hurting, one official said. The official explained that they believe the Russians would not have sent that message if they felt they were in a strong place on the battlefield. The note, known as a demarche, was sent earlier this week as the US administration was preparing to announce that it would be sending a new military aid package worth $800 million to the Ukrainians. The EU has also approved an additional 500 million euros for military equipment for Ukraine. For the first time since Russia’s invasion of Ukraine, the US is providing Kyiv with high-power capabilities that some Biden administration officials viewed as too much of an escalation risk a few short weeks ago. These include Mi-17 helicopters, 18 155 mm Howitzers and 300 more Switchblade drones. These types of weapons are designed for the type of fighting that’s likely to take place in the Donbas region — open terrain rather than urban and wooded areas. The US is also shipping 40,000 artillery rounds, but that amount could be expended within several days if fighting in the east grows heavier. During previous battles, Ukrainian forces fired thousands of artillery rounds in a day, a US official said Saturday. There are growing concerns about the need to get more ammunition, in particular artillery ammunition, to Ukrainian forces more rapidly, a US official said. The Ukrainian military and regional officials have said Russian attacks have intensified in Kharkiv, Luhansk and Donetsk regions in the east of the country as they prepare for a major ground offensive there. Going forward, US officials believe the likely Russia strategy is to move weapons and troops into eastern Ukraine from their current positions just north and then encircle and cut off Ukraine forces that are there, the official said. Defense Secretary Lloyd Austin and General Mark Milley are conducting daily phone calls with counterparts in the region to encourage them to ship more weapons and supplies to Ukraine as soon as possible. Serhii Haidai, head of the Luhansk region military administration, has warned civilians who remain in Luhansk to leave the area. “It is extremely dangerous to stay in the cities now. The shelling intensified,” he said. The Ukrainian armed forces General Staff said that “the main focus of the Russian enemy is on the regrouping and strengthening of troops” around Slobozhansky, an area that is a short distance south of Kharkiv. In the same area, according to the General Staff, Russian forces have concentrated up to 22 battalion tactical groups around Izium. A battalion tactical group normally comprises about 1,000 troops.